Fix previous change of FindThreadsCxx.cmake by copying needed source file from…

Fix previous change of FindThreadsCxx.cmake by copying needed source file from CMake installation, changing the file name extension only.

cmake/CheckForPthreads.cxx

-#include <stdio.h>
-#include <pthread.h>
-#include <unistd.h>
-
-void* runner(void*);
-
-int res = 0;
-#ifdef __CLASSIC_C__
-int main(){
-  int ac;
-  char*av[];
-#else
-int main(int ac, char*av[]){
-#endif
-  pthread_t tid[2];
-  pthread_create(&tid[0], 0, runner, (void*)1);
-  pthread_create(&tid[1], 0, runner, (void*)2);
-
-#if defined(__BEOS__) && !defined(__ZETA__) // (no usleep on BeOS 5.)
-  usleep(1); // for strange behavior on single-processor sun
-#endif
-
-  pthread_join(tid[0], 0);
-  pthread_join(tid[1], 0);
-  if(ac > 1000){return *av[0];}
-  return res;
-}
-
-void* runner(void* args)
-{
-  int cc;
-  for ( cc = 0; cc < 10; cc ++ )
-    {
-    printf("%d CC: %d\n", (int)args, cc);
-    }
-  res ++;
-  return 0;
-}

cmake/FindThreadsCxx.cmake

@@ -98,9 +98,10 @@ else()
       # If we did not found -lpthread, -lpthread, or -lthread, look for -pthread
       if("THREADS_HAVE_PTHREAD_ARG" MATCHES "^THREADS_HAVE_PTHREAD_ARG")
         message(STATUS "Check if compiler accepts -pthread")
+        configure_file ("${CMAKE_ROOT}/Modules/CheckForPthreads.c" "${CMAKE_BINARY_DIR}/CheckForPthreads.cxx" COPYONLY)
         try_run(THREADS_PTHREAD_ARG THREADS_HAVE_PTHREAD_ARG
           ${CMAKE_BINARY_DIR}
-          ${CMAKE_ROOT}/Modules/CheckForPthreads.cxx
+          ${CMAKE_BINARY_DIR}/CheckForPthreads.cxx
           CMAKE_FLAGS -DLINK_LIBRARIES:STRING=-pthread
           COMPILE_OUTPUT_VARIABLE OUTPUT)