compilers: clike: Deduplicate compile and link args from actually used arg list

Current behaviour is to loop over 'sys_args' list which contains both
included and ignored compiler arguments.
This could produce unexpected results when argument is both ignored and
deduplicated.
With the following changes, 'cleaned_sys_args' is used to ensure only
included args are deduplicated.

Example:

CFLAGS (or 'c_args' as Meson option) has '-I${includedir} -L${libdir}'
and LDFLAGS ('c_link_args') has '-L${libdir}'.
Given CFLAGS value is wrong: -L entry belongs to LDFLAGS and thus should
not be included in compiler argument list.
Since we have -L in 'sys_args' list this entry will not be included as
linker flag too!
This is definitely not our goal: wrong entry should just be ignored.

Some debug prints from Meson:

C_ARGS: ['-I/opt/x64-compile/include', '-L/opt/x64-compile/lib']
LINKER_ARGS: ['-L/opt/x64-compile/lib']
RESULT_CARGS: ['-I/opt/x64-compile/include', '-D_FILE_OFFSET_BITS=64']
RESULT_LDARGS: []

(this is captured during compiler.find_library() call)

And this is what we see after applying patch:

C_ARGS: ['-I/opt/x64-compile/include', '-L/opt/x64-compile/lib']
LINKER_ARGS: ['-L/opt/x64-compile/lib']
RESULT_CARGS: ['-I/opt/x64-compile/include', '-D_FILE_OFFSET_BITS=64']
RESULT_LDARGS: ['-L/opt/x64-compile/lib']

Author: Zaburunier

mesonbuild/compilers/mixins/clike.py

@@ -385,7 +385,7 @@ def _get_basic_compiler_args(self, mode: CompileCheckMode) -> T.Tuple[T.List[str
             sys_ld_args = self.environment.coredata.get_external_link_args(self.for_machine, self.language)
             # CFLAGS and CXXFLAGS go to both linking and compiling, but we want them
             # to only appear on the command line once. Remove dupes.
-            largs += [x for x in sys_ld_args if x not in sys_args]
+            largs += [x for x in sys_ld_args if x not in cleaned_sys_args]
 
         cargs += self.get_compiler_args_for_mode(mode)
         return cargs, largs