LSM: SafeSetID: selftest cleanup and prepare for GIDs

Add some notes on how to run the test, update the policy file paths to
reflect recent upstream changes, prepare test for adding GID testing.

Signed-off-by: Micah Morton <mortonm@chromium.org>

selftests: safesetid: Fix Makefile to set correct test program

Fix Makefile to set safesetid-test.sh to TEST_PROGS instead
of non existing run_tests.sh.

Without this fix, I got following error.
----
TAP version 13
1..1
# selftests: safesetid: run_tests.sh
# Warning: file run_tests.sh is missing!
not ok 1 selftests: safesetid: run_tests.sh
----

Fixes: c67e8ec03f3f ("LSM: SafeSetID: add selftest")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

selftests: safesetid: Move link library to LDLIBS

Move -lcap to LDLIBS from CFLAGS because it is a library
to be linked.

Without this, safesetid failed to build with link error
as below.

----
/usr/bin/ld: /tmp/ccL8rZHT.o: in function `drop_caps':
safesetid-test.c:(.text+0xe7): undefined reference to `cap_get_proc'
/usr/bin/ld: safesetid-test.c:(.text+0x107): undefined reference to `cap_set_flag'
/usr/bin/ld: safesetid-test.c:(.text+0x10f): undefined reference to `cap_set_proc'
/usr/bin/ld: safesetid-test.c:(.text+0x117): undefined reference to `cap_free'
/usr/bin/ld: safesetid-test.c:(.text+0x136): undefined reference to `cap_clear'
collect2: error: ld returned 1 exit status
----

Fixes: c67e8ec03f3f ("LSM: SafeSetID: add selftest")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

LSM: SafeSetID: add selftest

This patch adds a selftest for the SafeSetID LSM. The test requires
mounting securityfs if it isn't mounted, creating test users in
/etc/passwd, and configuring policies for the SafeSetID LSM through
writes to securityfs.

Signed-off-by: Micah Morton <mortonm@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>