KVM: selftests: Print the errno besides error-string in TEST_ASSERT

Print the errno besides error-string in TEST_ASSERT in the format of
"errno=%d - %s" will explicitly indicate that the string is an error
information. Besides, the errno is easier to be used for debugging
than the error-string.
Suggested-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20210330080856.14940-5-wangyanan55@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/lib/assert.c

@@ -71,9 +71,9 @@ test_assert(bool exp, const char *exp_str,
 
 		fprintf(stderr, "==== Test Assertion Failure ====\n"
 			"  %s:%u: %s\n"
-			"  pid=%d tid=%d - %s\n",
+			"  pid=%d tid=%d errno=%d - %s\n",
 			file, line, exp_str, getpid(), _gettid(),
-			strerror(errno));
+			errno, strerror(errno));
 		test_dump_stack();
 		if (fmt) {
 			fputs("  ", stderr);