MSVC: support -LIBPATH

Fixes mesonbuild#6101 (with a test), following up mesonbuild#5881

mesonbuild/compilers/mixins/visualstudio.py

@@ -217,7 +217,9 @@ def unix_args_to_native(cls, args: typing.List[str]) -> typing.List[str]:
             # -pthread is only valid for GCC
             if i in ('-mms-bitfields', '-pthread'):
                 continue
-            if i.startswith('-L'):
+            if i.startswith('-LIBPATH:'):
+                i = '/LIBPATH:' + i[9:]
+            elif i.startswith('-L'):
                 i = '/LIBPATH:' + i[2:]
             # Translate GNU-style -lfoo library name to the import library
             elif i.startswith('-l'):
@@ -250,7 +252,7 @@ def unix_args_to_native(cls, args: typing.List[str]) -> typing.List[str]:
     def native_args_to_unix(cls, args: typing.List[str]) -> typing.List[str]:
         result = []
         for arg in args:
-            if arg.startswith('/LIBPATH:'):
+            if arg.startswith(('/LIBPATH:', '-LIBPATH:')):
                 result.append('-L' + arg[9:])
             elif arg.endswith(('.a', '.lib')) and not os.path.isabs(arg):
                 result.append('-l' + arg)

run_unittests.py

@@ -3162,7 +3162,7 @@ def test_guessed_linker_dependencies(self):
         env = get_fake_env(testdirlib, self.builddir, self.prefix)
         if env.detect_c_compiler(MachineChoice.HOST).get_id() in {'msvc', 'clang-cl', 'intel-cl'}:
             # msvc-like compiler, also test it with msvc-specific flags
-            libdir_flags += ['/LIBPATH:']
+            libdir_flags += ['/LIBPATH:', '-LIBPATH:']
         else:
             # static libraries are not linkable with -l with msvc because meson installs them
             # as .a files which unix_args_to_native will not know as it expects libraries to use
@@ -3176,6 +3176,7 @@ def test_guessed_linker_dependencies(self):
 
         for libdir_flag in libdir_flags:
             # build library
+            self.new_builddir()
             self.init(testdirlib, extra_args=extra_args)
             self.build()
             self.install()