jit: Fix truncation of testsuite output [PR69435]

jit: Fix truncation of testsuite output [PR69435]

This 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).

This 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).

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

gcc/testsuite/
	PR jit/69435
	* jit.dg/jit.exp (fixed_host_execute): Fix regex patterns to
	always explicitly match newlines.