meson: Enable initialized-but-unused warning for MSVC

Reviewed-by: Yonggang Luo <luoyonggang@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19792>

meson.build

@@ -1137,6 +1137,7 @@ if cc.get_argument_syntax() == 'msvc'
     '/wd5105',  # macro expansion producing 'defined' has undefined behavior (winbase.h, need Windows SDK upgrade)
     '/we4020',  # Error when passing the wrong number of parameters
     '/we4024',  # Error when passing different type of parameter
+    '/we4189',  # 'identifier' : local variable is initialized but not referenced
     '/Zc:__cplusplus', #Set __cplusplus macro to match the /std:c++<version> on the command line
   ]
   c_args += cc.get_supported_arguments(_trial)

src/amd/addrlib/meson.build

@@ -68,7 +68,7 @@ endif
 cpp_args_addrlib += cpp.get_supported_arguments(
   ['-Wno-unused-variable', '-Wno-unused-local-typedefs',
    '-Wno-unused-but-set-variable', '-Wno-maybe-uninitialized',
-   '-Wno-self-assign']
+   '-Wno-self-assign', '/wd4189']
 )
 
 libamdgpu_addrlib = static_library(

src/util/macros.h

@@ -277,7 +277,7 @@ do {                       \
 #ifdef HAVE_FUNC_ATTRIBUTE_UNUSED
 #define UNUSED __attribute__((unused))
 #elif defined (_MSC_VER)
-#define UNUSED __pragma(warning(suppress:4100 4101))
+#define UNUSED __pragma(warning(suppress:4100 4101 4189))
 #else
 #define UNUSED
 #endif