Tests: fix RunCMake.Make test when run on systems with non-english locale

Set `LANG=C` in the environment so the output of `make` is predictable.

Fixes: #19689

Tests/RunCMake/Make/RunCMakeTest.cmake

@@ -26,10 +26,13 @@ function(run_VerboseBuild)
   endif()
   run_cmake_command(VerboseBuild-build ${CMAKE_COMMAND} --build . -v --clean-first)
   unset(RunCMake-stdout-file)
+  set(_backup_lang "$ENV{LANG}")
   if(MAKE_IS_GNU)
     set(RunCMake-stdout-file VerboseBuild-nowork-gnu-stdout.txt)
+    set(ENV{LANG} "C")
   endif()
   run_cmake_command(VerboseBuild-nowork ${CMAKE_COMMAND} --build . --verbose)
+  set(ENV{LANG} "${_backup_lang}")
 endfunction()
 run_VerboseBuild()