test_fips: two tweaks

  1. Ensure that the output is line buffered so that nothing is lost
     when tests fail.
  2. Check that FIPS_mode returns the expected mode so that we have
     evidence for this during testing.

Change-Id: Ib294e890a21e8002d5e2a646f08b49a03e645cb2
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/69487
Auto-Submit: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

util/fipstools/test_fips.c

@@ -50,6 +50,17 @@ static void hexdump(const void *a, size_t len) {
 int main(int argc, char **argv) {
   CRYPTO_library_init();
 
+  // Ensure that the output is line-buffered rather than fully buffered. When
+  // some of the tests fail, some of the output can otherwise be lost.
+  setvbuf(stdout, NULL, _IOLBF, 0);
+  setvbuf(stderr, NULL, _IOLBF, 0);
+
+  if (!FIPS_mode()) {
+    printf("Module not in FIPS mode\n");
+    goto err;
+  }
+  printf("Module is in FIPS mode\n");
+
   const uint32_t module_version = FIPS_version();
   if (module_version == 0) {
     printf("No module version set\n");