pick last compiler instead of first, will be overwritten by more advanced preferences as mentioned in the email group

lib/spack/spack/concretize.py

@@ -287,7 +287,7 @@ def concretize_compiler(self, spec):
             raise UnavailableCompilerVersionError(other_compiler)
             
         # copy concrete version into other_compiler
-        spec.compiler = matches[0].copy()
+        spec.compiler = matches[len(matches)-1].copy()
         assert(spec.compiler.concrete)
         return True  # things changed.