Port most of the Mono module build to Meson

Missing:
- Test platform: macOS (Should work but I've not tested yet.)
- Finish and test: Windows (Mostly done. Should require a few fixes, but I'm too lazy to reboot right now.)
- Finish and test: All non-desktop platforms (Blocked until implemented for the rest of Godot.)
  - NOTE: For android we were copying shared libs to `#platform/android/java/lib/libs`. How will this work with Meson (out-of-source builds)?

!!! Check TODOs and FIXMEs in 'modules/mono/meson.build'.

meson_options.txt

@@ -11,7 +11,7 @@ option('xaudio2', type: 'boolean', value: false, description: 'Enable the XAudio
 option('android_neon', type: 'boolean', value: true, description: 'Enable NEON support (armv7 only)')
 option('custom_modules', type: 'array', value: [], description: 'A list of comma-separated directory paths containing custom modules to build')
 # add text_server_fb to disabled modules
-option('disabled_modules', type: 'array', value: ['mono', 'text_server_fb'], description: 'A list of modules that are to be disabled')
+option('disabled_modules', type: 'array', value: ['text_server_fb'], description: 'A list of modules that are to be disabled')
 option('disable_all_modules', type: 'boolean', value: false, description: 'A boolean that disables ALL modules.')
 
 # Advanced options
@@ -54,7 +54,15 @@ option('builtin_graphite', type: 'boolean', value: true, description: 'Use the b
 option('builtin_icu', type: 'boolean', value: true, description: 'Use the built-in icu library')
 
 # Mono options
-option('mono_glue', type: 'boolean', value: true, description: 'Enable mono glue')
+
+option('mono_prefix', type: 'string', value: '', description: 'Path to the Mono installation directory for the target platform and architecture')
+option('mono_bcl', type: 'string', value: '', description: 'Path to a custom Mono BCL (Base Class Library) directory for the target platform')
+option('mono_static', type: 'combo', choices: ['auto', 'true', 'false'], value: 'auto', description: 'Statically link Mono')
+option('mono_glue', type: 'boolean', value: true, description: 'Build with the Mono glue sources')
+option('build_cil', type: 'boolean', value: true, description: 'Build C# solutions')
+option('copy_mono_root', type: 'boolean', value: true, description: 'Make a copy of the Mono installation directory to bundle with the editor')
+# TODO: It would be great if this could be detected automatically instead
+option('mono_bundles_zlib', type: 'combo', choices: ['auto', 'true', 'false'], value: 'auto', description: 'Specify if the Mono runtime was built with bundled zlib')
 
 # Javascript Options
 option('initial_wasm_memory', type: 'integer', value: 16, description: 'Initial WASM memory (in MiB)')
@@ -68,4 +76,4 @@ option('use_safe_heap', type: 'boolean', value: false, description: 'Use Emscrip
 option('javascript_eval', type: 'boolean', value: true, description: 'Enable JavaScript eval interface')
 option('threads_enabled', type: 'boolean', value: false, description: 'Enable WebAssembly Threads support (limited browser support)')
 option('gdnative_enabled', type: 'boolean', value: false, description: 'Enable WebAssembly GDNative support (produces bigger binaries)')
-option('use_closure_compiler', type: 'boolean', value: false, description: 'Use closure compiler to minimize JavaScript code')
+option('use_closure_compiler', type: 'boolean', value: false, description: 'Use closure compiler to minimize JavaScript code')

modules/mono/Directory.Build.targets

@@ -0,0 +1,15 @@
+<Project>
+    <Target Name="WriteMesonDepList" Condition=" '$(MesonDepListPath)' != '' ">
+        <Message Importance="High" Text="Writing to depfile ($(ProjectName)): $(MesonDepListPath)" />
+        <WriteLinesToFile
+            File="$(MesonDepListPath)"
+            Lines="%(Compile.FullPath);%(ProjectReference.FullPath);%(MesonWatchImport.FullPath)"
+            Overwrite="false"
+            Encoding="utf-8" />
+        <WriteLinesToFile
+            File="$(MesonDepListPath)"
+            Lines="$(ProjectPath)"
+            Overwrite="false"
+            Encoding="utf-8" />
+    </Target>
+</Project>

modules/mono/build_scripts/copy_file.py

@@ -0,0 +1,40 @@
+#!/usr/bin/python3
+
+import argparse
+from shutil import copy2
+
+
+# Only needed for the stamp file
+def touch(path):
+    import os
+    with open(path, 'a'):
+        os.utime(path, None)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description='Prints the specified environment variable')
+    parser.add_argument('src', type=str)
+    parser.add_argument('dst', type=str)
+    parser.add_argument('--stamp', type=str)
+
+    args = parser.parse_args()
+
+    # Only check if directory exists if copy fails
+
+    try:
+        copy2(args.src, args.dst)
+    except (IOError, FileNotFoundError) as e:
+        import errno
+        if isinstance(e, IOError) and e.errno != errno.ENOENT:
+            raise
+        import os.path
+        dst_dir = os.path.dirname(args.dst)
+        if os.path.isdir(dst_dir):
+            raise
+        import os
+        os.makedirs(dst_dir, exist_ok=True)
+        copy2(args.src, args.dst)
+
+    if args.stamp:
+        touch(args.stamp)

modules/mono/build_scripts/cs_glue_version.py

@@ -0,0 +1,44 @@
+#!/usr/bin/python3
+
+import argparse
+import sys
+
+# Whatever...
+try:
+    import run_msbuild
+except:
+    from . import run_msbuild
+
+
+def generate_header(version_header_dst: str, deplist: [str]):
+    import os
+
+    latest_mtime = 0
+    for filepath in deplist:
+        mtime = os.path.getmtime(filepath)
+        latest_mtime = mtime if mtime > latest_mtime else latest_mtime
+
+    glue_version = int(latest_mtime)  # The latest modified time will do for now
+
+    with open(version_header_dst, "w") as version_header:
+        version_header.write("/* THIS FILE IS GENERATED DO NOT EDIT */\n")
+        version_header.write("#ifndef CS_GLUE_VERSION_H\n")
+        version_header.write("#define CS_GLUE_VERSION_H\n\n")
+        version_header.write("#define CS_GLUE_VERSION UINT32_C(" + str(glue_version) + ")\n")
+        version_header.write("\n#endif // CS_GLUE_VERSION_H\n")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description='Generate C# glue version header')
+
+    run_msbuild.add_arguments_to_parser(parser)
+
+    args = parser.parse_args()
+
+    result = run_msbuild.run_msbuild_with_args(args)
+
+    if result.exit_code != 0:
+        sys.exit(result.exit_code)
+
+    generate_header(args.stamp, result.deplist)

modules/mono/build_scripts/mono_reg_utils.py → modules/mono/build_scripts/find_mono_in_winreg.py

@@ -1,3 +1,5 @@
+#!/usr/bin/python3
+
 import os
 import platform
 
@@ -62,52 +64,14 @@ def find_mono_root_dir(bits):
     return ""
 
 
-def find_msbuild_tools_path_reg():
-    import subprocess
-
-    vswhere = os.getenv("PROGRAMFILES(X86)")
-    if not vswhere:
-        vswhere = os.getenv("PROGRAMFILES")
-    vswhere += r"\Microsoft Visual Studio\Installer\vswhere.exe"
-
-    vswhere_args = ["-latest", "-products", "*", "-requires", "Microsoft.Component.MSBuild"]
-
-    try:
-        lines = subprocess.check_output([vswhere] + vswhere_args).splitlines()
-
-        for line in lines:
-            parts = line.decode("utf-8").split(":", 1)
-
-            if len(parts) < 2 or parts[0] != "installationPath":
-                continue
-
-            val = parts[1].strip()
+if __name__ == "__main__":
+    import argparse
+    parser = argparse.ArgumentParser(
+        description='Attempts to find the Mono install directory in the Windows Registry')
+    parser.add_argument('cpu_family', choices=['x86', 'x86_64'], type=str)
 
-            if not val:
-                raise ValueError("Value of `installationPath` entry is empty")
+    args = parser.parse_args()
 
-            # Since VS2019, the directory is simply named "Current"
-            msbuild_dir = os.path.join(val, "MSBuild\\Current\\Bin")
-            if os.path.isdir(msbuild_dir):
-                return msbuild_dir
-
-            # Directory name "15.0" is used in VS 2017
-            return os.path.join(val, "MSBuild\\15.0\\Bin")
-
-        raise ValueError("Cannot find `installationPath` entry")
-    except ValueError as e:
-        print("Error reading output from vswhere: " + e.message)
-    except OSError:
-        pass  # Fine, vswhere not found
-    except (subprocess.CalledProcessError, OSError):
-        pass
-
-    # Try to find 14.0 in the Registry
-
-    try:
-        subkey = r"SOFTWARE\Microsoft\MSBuild\ToolsVersions\14.0"
-        with _reg_open_key(winreg.HKEY_LOCAL_MACHINE, subkey) as hKey:
-            value = winreg.QueryValueEx(hKey, "MSBuildToolsPath")[0]
-            return value
-    except OSError:
-        return ""
+    res = find_mono_root_dir(bits='32' if args.cpu_family == 'x86' else '64')
+    if res:
+        print(res)