Fix Gasnet build to use gcc explicitly since Pal has wrong v. of cc.
Fix Gasnet build to use gcc explicitly since Pal has wrong v. of cc.

buaasun/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,uwsampa/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,buaasun/grappa,buaasun/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa