[rules_ios] Add static library variant to allow rewriting headers (#1)

Add an `apple_static_library` that lets us map source files to arbitrary
relative include paths by creating a link tree, and adding that link
tree to the deps of a main library.

This also uses apple_library instead of apple_framework as the framework
is frankly unnecessary for what we're trying to build for third party
deps.

Test Plan: Ported fmt locally to use this, and ran `clyde ios build`

Tasks:

https://app.asana.com/0/1203960884932166/1204190072048691 
https://app.asana.com/0/1203960884932166/1204190072362093

rules/library.bzl

@@ -1018,7 +1018,7 @@ def apple_library(name, library_tools = {}, export_private_headers = True, names
         _append_headermap_copts(swift_angle_bracket_hmap_name, "-I", additional_objc_copts, additional_swift_copts, additional_cc_copts)
 
     # Note: this line is intentionally disabled
-    if cpp_sources:
+    if cpp_sources and False:
         additional_cc_copts.append("-I.")
         native.objc_library(
             name = cpp_libname,

rules/static_library.bzl

@@ -0,0 +1,179 @@
+load("@bazel_skylib//lib:paths.bzl", "paths")
+load("//rules:library.bzl", "apple_library")
+
+def apple_static_library(
+        name,
+        apple_library = apple_library,
+        public_headers = [],
+        public_headers_to_name = {},
+        visibility = [],
+        testonly = False,
+        **kwargs):
+
+    """
+    A thin wrapper around `apple_library` that exposes a single target to depend on
+    and allows additionally exposing renamed headers.
+
+    public_headers_to_name is a dictionary that maps input files to their output
+    location within the link tree. This link tree then is added as a dep to the
+    final library. This allows us to effectively "move" headers and #include them
+    at whatever path we want.
+
+    Every other attribute is passed through to applie_library/objc_library as is
+    from **kwargs.
+
+    Examples:
+        In the case below, we declare "include/fmt/chorno.h" as a public header,
+        but we remap it so that '#include <fmt/chrono.h>' works.
+
+        ```
+		apple_static_library(
+			name = "Texture",
+			srcs = glob([
+				"Source/**/*.h",
+				"Source/**/*.mm",
+				"Source/TextKit/*.h",
+			]),
+			module_name = "AsyncDisplayKit",
+			platforms = {"ios": "9.0"},
+			public_headers = [
+				"Source/ASBlockTypes.h",
+				"Source/ASButtonNode+Private.h",
+				"Source/ASButtonNode+Yoga.h",
+				"Source/ASButtonNode.h",
+				"Source/ASCellNode.h",
+				"Source/ASCollectionNode+Beta.h",
+				"Source/ASCollectionNode.h",
+				"Source/ASCollections.h",
+				"Source/ASCollectionView.h",
+				"Source/ASCollectionViewLayoutFacilitatorProtocol.h",
+				"Source/ASCollectionViewProtocols.h",
+				"Source/ASConfiguration.h",
+				"Source/ASConfigurationDelegate.h",
+				"Source/ASConfigurationInternal.h",
+				"Source/ASContextTransitioning.h",
+				"Source/ASControlNode+Subclasses.h",
+				"Source/ASControlNode.h",
+				"Source/ASDisplayNode+Beta.h",
+				"Source/ASDisplayNode+Convenience.h",
+				"Source/ASDisplayNode+InterfaceState.h",
+				"Source/ASDisplayNode+LayoutSpec.h",
+				"Source/ASDisplayNode+Subclasses.h",
+				"Source/ASDisplayNode+Yoga.h",
+				...
+				"Source/Details/ASAbstractLayoutController.h",
+				"Source/Details/ASBasicImageDownloader.h",
+				"Source/Details/ASBatchContext.h",
+				...
+				"Source/Debug/AsyncDisplayKit+Tips.h",
+				"Source/TextKit/ASTextNodeTypes.h",
+				"Source/TextKit/ASTextKitComponents.h",
+			],
+			public_headers_to_name = {
+				"Source/ASBlockTypes.h": "Texture/AsyncDisplayKit/ASBlockTypes.h",
+				"Source/ASButtonNode+Private.h": "Texture/AsyncDisplayKit/ASButtonNode+Private.h",
+				"Source/ASButtonNode+Yoga.h": "Texture/AsyncDisplayKit/ASButtonNode+Yoga.h",
+				...
+				"Source/Details/ASAbstractLayoutController.h": "Texture/AsyncDisplayKit/ASAbstractLayoutController.h",
+				"Source/Details/ASBasicImageDownloader.h": "Texture/AsyncDisplayKit/ASBasicImageDownloader.h",
+				"Source/Details/ASBatchContext.h": "Texture/AsyncDisplayKit/ASBatchContext.h",
+				...
+				"Source/Debug/AsyncDisplayKit+Tips.h": "Texture/AsyncDisplayKit/AsyncDisplayKit+Tips.h",
+				"Source/TextKit/ASTextNodeTypes.h": "Texture/AsyncDisplayKit/ASTextNodeTypes.h",
+				"Source/TextKit/ASTextKitComponents.h": "Texture/AsyncDisplayKit/ASTextKitComponents.h",
+			},
+			sdk_dylibs = ["c++"],
+			sdk_frameworks = [
+				"AVFoundation",
+				"AssetsLibrary",
+				"CoreLocation",
+				"CoreMedia",
+				"MapKit",
+				"Photos",
+			],
+			visibility = ["//visibility:public"],
+			xcconfig = {
+				"CLANG_CXX_LANGUAGE_STANDARD": "c++11",
+				"CLANG_CXX_LIBRARY": "libc++",
+				"GCC_PREPROCESSOR_DEFINITIONS": [
+					"AS_USE_ASSETS_LIBRARY=1",
+					"AS_USE_MAPKIT=1",
+					"AS_USE_PHOTOS=1",
+					"AS_USE_VIDEO=1",
+				],
+			},
+			deps = ["@PINRemoteImage"],
+		)
+        ```
+    """
+
+    public_headers = public_headers
+
+    library = apple_library(
+        name = name,
+        public_headers = public_headers,
+        visibility=visibility,
+        testonly=testonly,
+        **kwargs
+    )
+
+    platforms = library.platforms if library.platforms else {}
+
+    extra_deps = []
+
+    # TODO(nmj): We'll likely need to add a way to set up a private headers link tree
+    #            that others can include as a dependency too. This is just a thing
+    #            that some Pods do.
+    if public_headers_to_name:
+        public_headers_symlinks_name = "{}_public_headers_symlinks".format(name)
+        _headers_symlinks(
+            name = public_headers_symlinks_name,
+            hdrs = public_headers_to_name,
+            visibility = visibility,
+        )
+        extra_deps.append(public_headers_symlinks_name)
+
+    native.objc_library(
+        name = name,
+        deps = library.deps + extra_deps,
+        data = [library.data] if library.data else [],
+        linkopts = library.linkopts,
+        testonly = kwargs.get("testonly", False),
+        visibility = visibility,
+    )
+
+def _headers_symlinks_impl(ctx):
+    if not ctx.attr.hdrs:
+        return []
+
+    outputs = []
+    public_headers_dir = None
+    for hdr, sub_path in ctx.attr.hdrs.items():
+        output = ctx.actions.declare_file(paths.join(ctx.attr.name, sub_path))
+        outputs.append(output)
+        if public_headers_dir == None:
+            public_headers_dir = output.path[:-(len(sub_path) + 1)]
+        ctx.actions.symlink(output = output, target_file = hdr.files.to_list()[0])
+
+    output_depset = depset(outputs)
+    return [
+        DefaultInfo(files = output_depset),
+        CcInfo(compilation_context = cc_common.create_compilation_context(
+            headers = output_depset,
+            includes = depset([
+                public_headers_dir,
+            ]),
+        )),
+        apple_common.new_objc_provider(),
+    ]
+
+_headers_symlinks = rule(
+    implementation = _headers_symlinks_impl,
+    doc = "Rule that actually creates symlink trees for header remapping",
+    attrs = {
+        "hdrs": attr.label_keyed_string_dict(
+            allow_files = True,
+            doc = "Mapping of source file paths to relative path where the file should life in the link tree"
+        ),
+    },
+)