Hello,

This patch fixes a bug in jit.exp which causes the DejaGnu output of the
libgccjit testsuite to be nondeterministically truncated. This bug was
copied from DejaGnu's own implementation of the host_execute function.
See the upstream bug report [0] where the maintainers point out that the
regex patterns in host_execute should (but don't currently) explicitly
match newlines to avoid relying on DejaGnu not reading more than one
line of the output (which is not guaranteed).

To reproduce the bug, run:

$ make check-jit RUNTESTFLAGS="jit.exp=test-arith-overflow.c"
$ grep -v iteration testsuite/jit/jit.sum

and you should see some lines that have been truncated (I see the word
iteration partially or fully truncated). Alternatively, simply run the
testsuite twice (saving a copy of testsuite/jit/jit.sum from the first
run) and diff the two jit.sum files to observe the random truncations to
the output.

This patch should make it easier to test jit patches in the future,
since it makes it possible to reliably compare the output of two jit.sum
files (as with the other tests in GCC).

Testing:
 * Ran the testsuite before and after the patch, observing that the only
   differences in jit.sum were in test-threads.c (nondeterministic test)
   and where the truncated output from the first run was no longer
   truncated.
 * Ran the testsuite twice after the patch, observing that the only
   differences in jit.sum between the two runs were in test-threads.c.

OK for master?

Thanks,
Alex

---

2020-07-20  Alex Coplan  <alex.coplan@arm.com>

gcc/testsuite/ChangeLog:

	* jit.dg/jit.exp (fixed_host_execute): Fix regex patterns to
	always explicitly match newlines.


[0] : https://debbugs.gnu.org/cgi/bugreport.cgi?bug=42399