Change fundersoring test with a more accurate regex to ensure the lack
of a trailing underscore, current TC is failing on AIX
Co-authored-by: Mark Danial <mark.danial@ibm.com>
There was a bug with the -funderscoring / -fno-underscoring options from (https://reviews.llvm.org/D140795) that prevented the driver option from controlling the underscoring behaviour and instead the behaviour could only be controlled by the pass option instead of the driver option. The driver test case did not catch the bug and also needed to be updated.
Reviewed By: awarzynski
Differential Revision: https://reviews.llvm.org/D155042