[AMDGPU][OpenMP] Do not attach -fcuda-is-device flag for AMDGPU OpenMP (#96909)

`-fcuda-is-device` flag is not used for OpenMP offloading for AMD GPUs
and it does not need to be added as clang cc1 option for OpenMP code.

Author: DominikAdamski

clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp

@@ -47,8 +47,6 @@ void AMDGPUOpenMPToolChain::addClangTargetOptions(
   assert(DeviceOffloadingKind == Action::OFK_OpenMP &&
          "Only OpenMP offloading kinds are supported.");
 
-  CC1Args.push_back("-fcuda-is-device");
-
   if (DriverArgs.hasArg(options::OPT_nogpulib))
     return;
 

clang/test/Driver/amdgpu-openmp-toolchain.c

@@ -7,7 +7,7 @@
 
 // verify the tools invocations
 // CHECK: "-cc1" "-triple" "x86_64-unknown-linux-gnu"{{.*}}"-emit-llvm-bc"{{.*}}"-x" "c"
-// CHECK: "-cc1" "-triple" "amdgcn-amd-amdhsa" "-aux-triple" "x86_64-unknown-linux-gnu"{{.*}}"-fcuda-is-device"{{.*}}"-target-cpu" "gfx906"
+// CHECK: "-cc1" "-triple" "amdgcn-amd-amdhsa" "-aux-triple" "x86_64-unknown-linux-gnu"{{.*}}"-target-cpu" "gfx906"
 // CHECK: "-cc1" "-triple" "x86_64-unknown-linux-gnu"{{.*}}"-emit-obj"
 // CHECK: clang-linker-wrapper{{.*}} "-o" "a.out"