[hipcc] Temporary add -D_OPENMP to clang options to workaround cmake issue (#1540)

* Temporary add -D_OPENMP to clang options in hipcc to allow using CMake OpenMP detection with hip-clang (until updated CMake version is available).

bin/hipcc

@@ -526,6 +526,13 @@ foreach $arg (@ARGV)
         $optArg = $arg;
     }
 
+    ## This is a temporary workaround for CMake detection of OpenMP support.
+    ## It should be removed when the OpenMP detection c++ test in CMake is updated
+    ## and corrected CMake version is available.
+    if((defined $HIP_COMPILER) and ($HIP_COMPILER eq "clang") and ($arg eq '-fopenmp')) {
+        $HIPCXXFLAGS .= " -D_OPENMP "
+    }
+
     ## process linker response file for hip-clang
     ## extract object files from static library and pass them directly to
     ## hip-clang in command line.