Tests: Disable broken FindPkgConfig test cases for Windows

The Windows implementation of these tests have been found to not
handle Windows paths and path separators properly in a number of
areas. The whole approach taken in these tests appears dubious, so
they may need to be significantly rewritten. Disable them until then
so we don't get false positives.

Issue: #22031

Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake

@@ -7,13 +7,18 @@ set(ENV{CMAKE_FRAMEWORK_PATH} "")
 
 run_cmake(PkgConfigDoesNotExist)
 
-run_cmake(FindPkgConfig_CMP0126_NEW)
-run_cmake(FindPkgConfig_NO_PKGCONFIG_PATH)
-run_cmake(FindPkgConfig_PKGCONFIG_PATH)
-run_cmake(FindPkgConfig_PKGCONFIG_PATH_NO_CMAKE_PATH)
-run_cmake(FindPkgConfig_PKGCONFIG_PATH_NO_CMAKE_ENVIRONMENT_PATH)
+if(NOT WIN32)
+  # FIXME: The Windows implementation of these tests do not work.
+  #        They are disabled until they can be updated to a working state.
+  run_cmake(FindPkgConfig_CMP0126_NEW)
+  run_cmake(FindPkgConfig_NO_PKGCONFIG_PATH)
+  run_cmake(FindPkgConfig_PKGCONFIG_PATH)
+  run_cmake(FindPkgConfig_PKGCONFIG_PATH_NO_CMAKE_PATH)
+  run_cmake(FindPkgConfig_PKGCONFIG_PATH_NO_CMAKE_ENVIRONMENT_PATH)
+  run_cmake(FindPkgConfig_GET_MATCHING_ARGN)
+endif()
+
 run_cmake(FindPkgConfig_extract_frameworks)
-run_cmake(FindPkgConfig_GET_MATCHING_ARGN)
 
 if(APPLE)
   run_cmake(FindPkgConfig_extract_frameworks_target)