PR for adding AMDGPU timing utils for benchmarking.
I was not able to test this code since I do not have an AMD GPU, but I
was able to successfully compile this code using
-DRUNTIMES_amdgcn-amd-amdhsa_LIBC_GPU_TEST_ARCHITECTURE=gfx90a
-DRUNTIMES_amdgcn-amd-amdhsa_LIBC_GPU_LOADER_EXECUTABLE=echo
-DRUNTIMES_amdgcn_amd-amdhsa_LIBC_GPU_TARGET_ARCHITECTURE=gfx90a to
force the code to compile without having an AMD gpu on my machine.
@jhuber6
PR for adding microbenchmarking infrastructure for NVPTX. `nvlink`
cannot perform LTO, so we cannot inline `libc` functions and this
function call overhead is not adjusted for during microbenchmarking.
