Add CRYPTO_has_asm.

This function will return whether BoringSSL was built with
OPENSSL_NO_ASM. This will allow us to write a test in our internal
codebase which asserts that normal builds should always have assembly
code included.

Change-Id: Ib226bf63199022f0039d590edd50c0cc823927b9
Reviewed-on: https://boringssl-review.googlesource.com/7960
Reviewed-by: David Benjamin <davidben@google.com>

crypto/crypto.c

@@ -131,6 +131,14 @@ int CRYPTO_is_confidential_build(void) {
 #endif
 }
 
+int CRYPTO_has_asm(void) {
+#if defined(OPENSSL_NO_ASM)
+  return 0;
+#else
+  return 1;
+#endif
+}
+
 const char *SSLeay_version(int unused) {
   return "BoringSSL";
 }

include/openssl/crypto.h

@@ -50,6 +50,10 @@ OPENSSL_EXPORT void CRYPTO_library_init(void);
  * internal version of BoringSSL. */
 OPENSSL_EXPORT int CRYPTO_is_confidential_build(void);
 
+/* CRYPTO_has_asm returns one unless BoringSSL was built with OPENSSL_NO_ASM,
+ * in which case it returns zero. */
+OPENSSL_EXPORT int CRYPTO_has_asm(void);
+
 
 /* Deprecated functions. */