[HIP] Fix visibility of __hip_fatbin

[yaxunl]

Summary

In -fgpu-rdc case, fat binary is embedded as global variable __hip_fatbin.
It needs to have protected visibility to avoid conflict between shared
libraries.

[scchan]

LGTM

clang/lib/Driver/ToolChains/HIP.cpp

void AMDGCN::Linker::constructGenerateObjFileFromHIPFatBinary(
   llvm::raw_string_ostream ObjStream(ObjBuffer);
 
   // Add MC directives to embed target binaries. We ensure that each
   // section and image is 16-byte aligned. This is not mandatory, but
   // increases the likelihood of data to be aligned with a cache block
   // in several main host machines.
   ObjStream << "#       HIP Object Generator\n";
   ObjStream << "# *** Automatically generated by Clang ***\n";
+  ObjStream << "  .protected __hip_fatbin\n";
   ObjStream << "  .type __hip_fatbin,@object\n";
   ObjStream << "  .section .hip_fatbin,\"a\",@progbits\n";
   ObjStream << "  .globl __hip_fatbin\n";
   ObjStream << "  .p2align " << llvm::Log2(llvm::Align(HIPCodeObjectAlign))
             << "\n";
   ObjStream << "__hip_fatbin:\n";
   ObjStream << "  .incbin \"" << BundleFile << "\"\n";
   ObjStream.flush();

clang/test/Driver/hip-toolchain-rdc.hip

 // REQUIRES: clang-driver
 // REQUIRES: x86-registered-target
 // REQUIRES: amdgpu-registered-target
 
 // RUN: %clang -### -target x86_64-linux-gnu \
 // RUN:   -x hip --cuda-gpu-arch=gfx803 --cuda-gpu-arch=gfx900 \
 // RUN:   --hip-device-lib=lib1.bc --hip-device-lib=lib2.bc \
 // RUN:   --hip-device-lib-path=%S/Inputs/hip_multiple_inputs/lib1 \
 // RUN:   --hip-device-lib-path=%S/Inputs/hip_multiple_inputs/lib2 \
 // RUN:   -fuse-ld=lld -fgpu-rdc -nogpuinc \
 // RUN:   -fhip-dump-offload-linker-script \
 // RUN:   %S/Inputs/hip_multiple_inputs/a.cu \
 // RUN:   %S/Inputs/hip_multiple_inputs/b.hip \
 // RUN: 2>&1 | FileCheck %s
 
 // check code object alignment in dumped llvm-mc input
+// CHECK: .protected __hip_fatbin
 // CHECK: .p2align 12
 
 // emit objects for host side path
 // CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "x86_64-unknown-linux-gnu"
 // CHECK-SAME: "-aux-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-emit-obj"
 // CHECK-SAME: {{.*}} "-main-file-name" "a.cu"
 // CHECK-SAME: "-fgpu-rdc"