[libc] Do not include GPU system libraries for integration tests

[jhuber6]

Summary

These should have -nogpulib but do not inherit it from anywhere else.
Add it in to prevent it from being pulled in as these compilations are
supposed to be 100% freestanding.

[JonChesterfield]

Might be a subset of D153581

[jhuber6]

Updating for the other stuff

[jhuber6]

Turns out that this picks it up from add_object_library.

libc/test/IntegrationTest/CMakeLists.txt

 if(LIBC_GPU_TARGET_ARCHITECTURE_IS_AMDGPU)
   set(TEST_COMPILE_FLAGS
+    -nogpulib
     -mcpu=${LIBC_GPU_TARGET_ARCHITECTURE}
     -emit-llvm # AMDGPU's intermediate object file format is bitcode.
     --target=${LIBC_GPU_TARGET_TRIPLE}
   )
 elseif(LIBC_GPU_TARGET_ARCHITECTURE_IS_NVPTX)
   set(TEST_COMPILE_FLAGS
+    -nogpulib
     -march=${LIBC_GPU_TARGET_ARCHITECTURE}
     --target=${LIBC_GPU_TARGET_TRIPLE}
     --cuda-path=${LIBC_CUDA_ROOT}
   )
 endif()
 
 add_object_library(
   test