Add CHECK_OPENMP_ENV environment variable which will be passed to environment
variables for test (make check-* target). This provides a handy way to
exercise various openmp code with different settings during development.
For example, to change default barrier pattern:
```
$ env CHECK_OPENMP_ENV="KMP_FORKJOIN_BARRIER_PATTERN=hier,hier \
KMP_PLAIN_BARRIER_PATTERN=hier,hier \
KMP_REDUCTION_BARRIER_PATTERN=hier,hier" \
ninja check-openmp
```
Even with this, each test can set appropriate environment variables if needed
as before.
Also, this commit adds missing documention about how to run tests in README.
Patch provided by t-msn
Differential Revision: https://reviews.llvm.org/D122645
Summary:
`config.test_extra_flags` is passed in from `lit.site.cfg.in` files, but they're not used in the LIT configs. This variable can be useful for distros which don't have the standard c/c++ headers in the default search paths. Since the tests run clang on c/c++ source code, we rely on `test_extra_flags` to pass in the necessary header files.
This is a similar setup that's also done in litomptarget https://github.com/llvm/llvm-project/blob/master/openmp/libomptarget/test/lit.cfg#L42 and openmp/runtime.
Reviewers: jdoerfert, jdenny, protze.joachim
Reviewed By: jdoerfert
Subscribers: yaxunl, guansong, sstefan1, openmp-commits
Tags: #openmp
Differential Revision: https://reviews.llvm.org/D82516
