BUG/MEDIUM: threads: Disable the workaround to load libgcc_s on macOS

BUG/MEDIUM: threads: Disable the workaround to load libgcc_s on macOS

Don't use the workaround to load libgcc_s on macOS. It is not needed
there, and it causes issues, as recent macOS dislike processes that fork
after threads where created (and the workaround creates a temporary
thread). This fixes crashes on macOS at least when using master-worker,
and using the system resolver.

This should fix Github issue #3035

This should be backported up to 2.8.

(cherry picked from commit f8e9545f700a4e3799bbac4cd1c94989b9c1fb61)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
(cherry picked from commit 0d87b8343f8780c1c677dd282dc7648cf038a00a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit ba9ee8147702b5cc5c400b7521afc2f13659eb2c)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>