[FileCheck] Make FILECHECK_OPTS useful for its test suite

Authored by jdenny on Nov 20 2019, 2:12 PM.


[FileCheck] Make FILECHECK_OPTS useful for its test suite

Without this patch, FILECHECK_OPTS isn't propagated to FileCheck's
test suite so that FILECHECK_OPTS doesn't inadvertently affect test
results by affecting the output of FileCheck calls under test. As a
result, FILECHECK_OPTS is useless for debugging FileCheck's test

In llvm/test/FileCheck/lit.local.cfg, this patch provides a new
subsitution, %ProtectFileCheckOutput, to address this problem for
both FILECHECK_OPTS and the deprecated
FILECHECK_DUMP_INPUT_ON_FAILURE. The rest of the patch uses
%ProtectFileCheckOutput throughout the test suite

Fixes PR40284.

Reviewed By: probinson, thopre

Differential Revision: https://reviews.llvm.org/D65121