try_compile: Cleanup temporary directories (#13160)

Since commit 4fbdce2b (try_compile: Use random executable file name,
2012-02-13) a different <target>.dir is used for each try-compile.
Cleanup the directories as well as their content to avoid accumulating
leftover temporary directories.

Source/cmCoreTryCompile.cxx

@@ -404,6 +404,7 @@ void cmCoreTryCompile::CleanupFiles(const char* binDir)
         if(cmSystemTools::FileIsDirectory(fullPath.c_str()))
           {
           this->CleanupFiles(fullPath.c_str());
+          cmSystemTools::RemoveADirectory(fullPath.c_str());
           }
         else
           {