external/conscrypt: control binary-field EC with OPENSSL_NO_EC2M.

OpenSSL supports many feature #defines to disable things. One of them is
OPENSSL_NO_EC2M, which BoringSSL also defines because it doesn't support
binary fields.

This change alters the guard around the binary-field call to check
OPENSSL_NO_EC2M rather than OPENSSL_IS_BORINGSSL. This is a no-op for
BoringSSL because it already defines both, but it'll allow OpenSSL built
without binary-field code to function too.

Change-Id: I46b74827ad6b2a43799ef62baf2832645e4865b4
1 file changed