selftests/bpf: Better error messages for ima_setup.sh failures

The current implementation uses the CHECK_FAIL macro which does not
provide useful error messages when the script fails. Use the CHECK macro
instead and provide more descriptive messages to aid debugging.
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210322170720.2926715-1-kpsingh@kernel.org

tools/testing/selftests/bpf/prog_tests/test_ima.c

@@ -68,7 +68,8 @@ void test_test_ima(void)
 		goto close_prog;
 
 	snprintf(cmd, sizeof(cmd), "./ima_setup.sh setup %s", measured_dir);
-	if (CHECK_FAIL(system(cmd)))
+	err = system(cmd);
+	if (CHECK(err, "failed to run command", "%s, errno = %d\n", cmd, errno))
 		goto close_clean;
 
 	err = run_measured_process(measured_dir, &skel->bss->monitored_pid);
@@ -81,7 +82,8 @@ void test_test_ima(void)
 
 close_clean:
 	snprintf(cmd, sizeof(cmd), "./ima_setup.sh cleanup %s", measured_dir);
-	CHECK_FAIL(system(cmd));
+	err = system(cmd);
+	CHECK(err, "failed to run command", "%s, errno = %d\n", cmd, errno);
 close_prog:
 	ima__destroy(skel);
 }