Fix X25519 on OS X when using build systems other than CMake.

Assembly code for X25519 wasn't included on OS X when built with
build systems other than CMake, which lead to a SIGTRAP due to a
missing x25519_x86_64.

Reported by Gurgen Hrachyan.

Change-Id: Ib6026f31cce0405ec3e75d8a52bf0940e57c62c8
Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Reviewed-on: https://boringssl-review.googlesource.com/8111
Reviewed-by: David Benjamin <davidben@google.com>

util/generate_build_files.py

@@ -45,6 +45,9 @@ NON_PERL_FILES = {
     ('linux', 'x86_64'): [
         'src/crypto/curve25519/asm/x25519-asm-x86_64.S',
     ],
+    ('mac', 'x86_64'): [
+        'src/crypto/curve25519/asm/x25519-asm-x86_64.S',
+    ],
 }