build: OpenSSL EC detection fails on macOS

[fanquake]

./configure --enable-openssl-tests
...
checking for libcrypto... yes
checking for main in -lcrypto... yes
checking for EC functions in libcrypto... no
configure: error: OpenSSL tests requested but OpenSSL with EC support is not available

config.log

configure:14672: checking for EC functions in libcrypto
configure:14696: gcc -c -O2 -fvisibility=hidden -std=c89 -pedantic -Wall -Wextra -Wcast-align -Wnested-externs -Wshadow -Wstrict-prototypes -Wno-unused-function -Wno-long-long -Wno-overlength-strings -W -g  conftest.c >&5
conftest.c:36:14: fatal error: 'openssl/ec.h' file not found
    #include <openssl/ec.h>
             ^~~~~~~~~~~~~~
1 error generated.

I can PR a fix shortly if no-one beats me to it.

[sipa]

Well do you have that file?

[fanquake]

Well do you have that file?

Yes, but it needs to come from the brew installed OpenSSL. Which isn't being used during this check.