compilers: Do not pass -fuse-ld=lld via -Wl,

`-fuse-ld=` is a driver option for selection of a linker; it shall not be
passed to a linker with `-Wl,`.

For the Microsoft compiler and linker, the options for the compiler and those
for the linker are separated by `/LINK`, which looks like `cl /cl-options ...
/link /link-options ...`. Formally, they are passed in the same command line.
When Clang is invoking the Microsoft linker or a Microsoft-style linker (that
is, LLD-LINK), every linker option has to prefixed by `-Wl,` or `-Xlink`.

Previously, using Clang-CL and LLD-LINK, given:

   cc = meson.get_compiler('c')
   assert(cc.has_link_argument('/LTCG'))

This code failed to detect the `/LTCG` option, because `-fuse-ld=lld` was
passed to the linker, as an invalid option:

   Command line: `clang E:\lh_mouse\Desktop\t\build\meson-private\tmpg0221fee\testfile.c -o E:\lh_mouse\Desktop\t\build\meson-private\tmpg0221fee\output.exe -D_FILE_OFFSET_BITS=64 -O0 -Werror=implicit-function-declaration -Wl,-WX -Wl,/LTCG -Wl,-fuse-ld=lld` -> 4044
   stdout:
   LINK : warning LNK4044: unrecognized option '/fuse-ld=lld'; ignored
   LINK : error LNK1218: warning treated as error; no output file generated

However, it should be noted that not all LINK options can be passed with
`-Wl,`. The `/subsystem:windows,6.1` option has a comma, which would be
converted to a space. Therefore, this option must be passed as
`-Xlinker -subsystem:windows,6.1`. This issue is not addressed in this commit.

Signed-off-by: LIU Hao <lh_mouse@126.com>

mesonbuild/compilers/mixins/clang.py

@@ -187,7 +187,7 @@ def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.
 
     def linker_to_compiler_args(self, args: T.List[str]) -> T.List[str]:
         if isinstance(self.linker, (ClangClDynamicLinker, MSVCDynamicLinker)):
-            return [flag if flag.startswith('-Wl,') else f'-Wl,{flag}' for flag in args]
+            return [flag if flag.startswith('-Wl,') or flag.startswith('-fuse-ld=') else f'-Wl,{flag}' for flag in args]
         else:
             return args