[testsuite] Remove bashism from libbacktrace/allocfail.sh

[testsuite] Remove bashism from libbacktrace/allocfail.sh

Test-case libbacktrace/allocfail.sh contains bashism "set -o pipefail", which
makes the script fail on ubuntu 18.04, which links /bin/sh to /bin/dash.

Fix this by removing the "set -o pipefail".

Tested by running the test-case with dash on x86_64-linux.

2018-12-14  Tom de Vries  <tdevries@suse.de>

	PR testsuite/88491
	* allocfail.sh: Remove "set -o pipefail".

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@267127 138bc75d-0d04-0410-961f-82ee72b054a4