test: copy libgcc_s.so.1 to TPM2 test image on Debian-like systems

test: copy libgcc_s.so.1 to TPM2 test image on Debian-like systems

On Ubuntu, cryptsetup does not link against libgcc_s.so.1 which leads to
the following test failure in TEST-70-TPM2:

 systemd[1]: Starting testsuite-70.service...
 systemd[329]: testsuite-70.service: Executing: /usr/lib/systemd/tests/testdata/units/testsuite-70.sh
 testsuite-70.sh[329]: + export SYSTEMD_LOG_LEVEL=debug
 testsuite-70.sh[329]: + SYSTEMD_LOG_LEVEL=debug
 testsuite-70.sh[329]: + img=/var/tmp/test.img
 testsuite-70.sh[329]: + dd if=/dev/zero of=/var/tmp/test.img bs=1024k count=20 status=none
 testsuite-70.sh[329]: + echo -n passphrase
 testsuite-70.sh[329]: + cryptsetup luksFormat -q --use-urandom /var/tmp/test.img /tmp/passphrase
 testsuite-70.sh[333]: libgcc_s.so.1 must be installed for pthread_exit to work
 testsuite-70.sh[329]: /usr/lib/systemd/tests/testdata/units/testsuite-70.sh:
     line 12: 333 Aborted (core dumped) cryptsetup luksFormat -q --use-urandom $img /tmp/passphrase

To fix this, manually install libgcc_s.so.1 to the test image if running
on Debian-like systems.