scons: Explicitly add librt to scons

gem5 uses the `shm_open()` funciton from <sys/mman.h>.
This function requires linking to librt.

JIRA: https://gem5.atlassian.net/browse/GEM5-1015

Change-Id: I461400e3cb7474a80a995b264af2e03b19fea29c
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47659
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed