Disable BlindingCacheConcurrency on FreeBSD.

Per the bug discussion, FreeBSD seems to default to a cap of 1500
threads per process. Just turn the test off.

But enable the test unconditionally if building with TSan. With TSan on,
we only spawn two threads, which should be within everyone's bounds.

Fixed: 603
Change-Id: Ic8c49e5ce7c3f2d09487debc72b7e4c54b04a77c
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/59445
Reviewed-by: Adam Langley <agl@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

crypto/rsa_extra/rsa_test.cc

@@ -1215,8 +1215,10 @@ TEST(RSATest, Threads) {
 // platforms when running tests standalone via all_tests.go.
 //
 // Additionally, even when running disabled tests standalone, limit this to
-// x86_64. On other platforms, this test hits resource limits or is too slow.
-#if defined(OPENSSL_X86_64)
+// x86_64. On other platforms, this test hits resource limits or is too slow. We
+// also disable on FreeBSD. See https://crbug.com/boringssl/603.
+#if defined(OPENSSL_TSAN) || \
+    (defined(OPENSSL_X86_64) && !defined(OPENSSL_FREEBSD))
 TEST(RSATest, DISABLED_BlindingCacheConcurrency) {
   bssl::UniquePtr<RSA> rsa(
       RSA_private_key_from_bytes(kKey1, sizeof(kKey1) - 1));
@@ -1251,6 +1253,6 @@ TEST(RSATest, DISABLED_BlindingCacheConcurrency) {
     thread.join();
   }
 }
-#endif  // X86_64
+#endif  // TSAN || (X86_64 && !FREEBSD)
 
 #endif  // THREADS