add patchelf as a required package in fbgemm_gpu/requirements.txt (pytorch#662)

Summary:
Pull Request resolved: facebookresearch/FBGEMM#662

As https://github.com/pytorch/FBGEMM/blob/4f620223837d68303097775db0afbcff8013603d/.github/scripts/fbgemm_gpu_postbuild.bash#L20 uses `patchelf`, it should be in requirements.txt

X-link: pytorch#3574

Reviewed By: spcyppt

Differential Revision: D68224847

Pulled By: q10

fbshipit-source-id: 5d91bed8aafa1db533c01df03ce33b4f043cb884

Author: liligwu

fbgemm_gpu/requirements.txt

@@ -23,3 +23,4 @@ scikit-build
 setuptools
 setuptools_git_versioning
 tabulate
+patchelf