selftest: show values when ASSERT_STREQ fails
Rework ASSERT_STREQ so that it prints the actual and expected values
to stderr when it fails (by moving it to a helper function).
gcc/ChangeLog:
* selftest.c (selftest::fail_formatted): New function.
(selftest::assert_streq): New function.
* selftest.h (selftests::fail_formatted): New decl.
(selftest::assert_streq): New decl.
(ASSERT_STREQ): Reimplement in terms of selftest::assert_streq.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@237404 138bc75d-0d04-0410-961f-82ee72b054a4