enable example_compiler_gym_service unit tests in CI

[mostafaelhoushi]

Let's do things one step at a time.
In this PR I checked out one file from https://github.com/facebookresearch/CompilerGym/pull/642/files# that doesn't require external files, binaries, or benchmarks and making sure it passes in CI.

[codecov-commenter]

Codecov Report

Merging #699 (977c64a) into development (9ad5fbb) will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           development     #699   +/-   ##
============================================
  Coverage        88.64%   88.64%           
============================================
  Files              131      131           
  Lines             7926     7926           
============================================
  Hits              7026     7026           
  Misses             900      900           

Impacted Files	Coverage Δ
compiler_gym/views/observation_space_spec.py	82.85% <0.00%> (-2.86%)	⬇️
compiler_gym/views/observation.py	97.29% <0.00%> (-2.71%)	⬇️
...loop_tool/service/loop_tool_compilation_session.py	87.83% <0.00%> (-2.03%)	⬇️
compiler_gym/envs/llvm/datasets/cbench.py	79.42% <0.00%> (-1.09%)	⬇️
compiler_gym/envs/gcc/service/gcc_service.py	97.06% <0.00%> (+0.36%)	⬆️
compiler_gym/service/connection.py	78.66% <0.00%> (+1.00%)	⬆️
compiler_gym/spaces/reward.py	80.70% <0.00%> (+7.01%)	⬆️

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[mostafaelhoushi]

@ChrisCummins : this CI seems to pass. Can we merge it? It just copied the env_tests.py unit tests to a file that can run in test-cmake-linux.

Before this PR, those test cases are not covered by CI.

[mostafaelhoushi]

The CI jobs that are red are not related to this PR

[ChrisCummins]

LGTM thanks @mostafaelhoushi!