Commit 4bb18b04 added _GNU_SOURCE to jq's Makefile to fix a segfault.
This has since been fixed upstream, so this commit backports the upstream
patch instead. This keeps things closer to upstream, and it will prevent
the Makefile from containing a redundant fix once upstream releases the
next version.
Signed-off-by: W. Michael Petullo <mike@flyn.org>
