Link with pytorch/xla when build for Linux

[wangkuiyi]

This change refactorized cgotorch/build.sh. In two cases, it builds libcgotorch.so for Linux: (1) Linux and no CUDA, and (2) Linux, with CUDA, but unsupported version. When it builds for Linux, it always link the pre-built pytorch/xla.

I will add wrappers and example code in the next PR.

[codecov]

Codecov Report

Merging #289 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #289   +/-   ##
========================================
  Coverage    80.58%   80.58%           
========================================
  Files           34       34           
  Lines         1638     1638           
========================================
  Hits          1320     1320           
  Misses         253      253           
  Partials        65       65           

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