Add guards for the architecture and OPENSSL_NO_ASM to
the assembly-language files in crypto/curve25519/asm.
The Dart compilation of BoringSSL includes all files,
because the architecture is not known when gyp is run.
Change-Id: I66f5ae525266b63b0fe3a929012b771d545779b5
Reviewed-on: https://boringssl-review.googlesource.com/7030
Reviewed-by: Adam Langley <agl@google.com>
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>