[CUDA] Allow parsing of host and device code simultaneously.

* adds -aux-triple option to specify target triple
 * propagates aux target info to AST context and Preprocessor
 * pulls in target specific preprocessor macros.
 * pulls in target-specific builtins from aux target.
 * sets appropriate host or device attribute on builtins.

Differential Revision: http://reviews.llvm.org/D12917

llvm-svn: 248299

clang/lib/Frontend/CompilerInvocation.cpp

@@ -975,6 +975,9 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
 
   Opts.OverrideRecordLayoutsFile
     = Args.getLastArgValue(OPT_foverride_record_layout_EQ);
+  Opts.AuxTriple =
+      llvm::Triple::normalize(Args.getLastArgValue(OPT_aux_triple));
+
   if (const Arg *A = Args.getLastArg(OPT_arcmt_check,
                                      OPT_arcmt_modify,
                                      OPT_arcmt_migrate)) {