igt_command_line.sh: Abort if run as root

`ninja test` invokes igt_command_line.sh for each test binary to check
the behavior of some of the switches. One of the verified things is that
the test exists with non-zero status when requesting invalid subtest.

`--run-subtest` results in igt_fixtures being executed - this fiddles
with the device and sysfs knobs.

Let's exit early, if we are root, to save people form unintentional
side-effects and strange failures.

Cc: Petri Latvala <petri.latvala@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/igt_command_line.sh

@@ -100,6 +100,10 @@ check_test ()
 	./$test --run-subtest invalid-subtest > /dev/null 2>&1 && fail $test
 }
 
+if [ "$EUID" -eq 0 ]; then
+    fail "Don't run $0 as root. It executes igt_fixture blocks."
+fi
+
 TESTLISTFILE="$tests_dir/test-list.txt"
 if [ ! -r "$TESTLISTFILE" ]; then
 	tests_dir="tests"