Include 'asm' in the name of X25519 asm sources.

Some build systems don't like two targets with the same base name and
the curve25519 code had x25519-x86_64.[Sc].

Change-Id: If8382eb84996d7e75b34b28def57829d93019cff
Reviewed-on: https://boringssl-review.googlesource.com/6878
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/util/generate_build_files.py b/util/generate_build_files.py
index 4a78005..6321c5c 100644
--- a/util/generate_build_files.py
+++ b/util/generate_build_files.py
@@ -41,7 +41,7 @@
     ('linux', 'arm'): [
         'src/crypto/chacha/chacha_vec_arm.S',
         'src/crypto/cpu-arm-asm.S',
-        'src/crypto/curve25519/asm/x25519-arm.S',
+        'src/crypto/curve25519/asm/x25519-asm-arm.S',
         'src/crypto/poly1305/poly1305_arm_asm.S',
     ],
 }