When compiling for macOS, where users will likely have OpenSSL installed
via brew, rather than available on the system, use brew --prefix to
figure out where OpenSSL is, and then augment the pkg-config path so
that libs are found.
Since commit 506df426dbeb0187bbd3654bd286b4100628fb16, OPENSSL_INCS is
added to CPPFLAGS without any white space, as a result openssl detection
fails on:
configure:10395: checking openssl/ssl.h usability
configure:10395: /home/fabrice/buildroot-test/buildroot/output/host/bin/riscv32-linux-gcc -c -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -Wall -fno-strict-aliasing -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64-I/home/fabrice/buildroot-test/buildroot/output/host/bin/../riscv32-buildroot-linux-gnu/sysroot/usr/include conftest.c >&5
<command-line>:0:0: warning: "_FILE_OFFSET_BITS" redefined
<command-line>:0:0: note: this is the location of the previous definition
<command-line>:0:23: error: division by zero in #if
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>