PR27799: [OpenCL] Clang fails to compile libclc

[yaxunl]

Summary

libclc fails to build due to some supported OpenCL extensions are not added to nvptx target.

[Anastasia]

Do we have any test for this? Would be nice to add one if possible.

[yaxunl]

This patch was superseded by http://reviews.llvm.org/D20389

lib/Basic/Targets.cpp

 
     return GPU != GK_NONE;
   }
+  void setSupportedOpenCLOpts() override {
+    auto &Opts = getSupportedOpenCLOpts();
+    Opts.cl_clang_storage_class_specifiers = 1;
+    Opts.cl_khr_byte_addressable_store = 1;
+    Opts.cl_khr_fp64 = 1;
+ }
 };
 
 const Builtin::Info NVPTXTargetInfo::BuiltinInfo[] = {