unix: set OPENSSLDIR to /private/etc/ssl on Apple platforms

This is the directory that system OpenSSL uses and what Apple's
Python uses.

By pointing our OpenSSL at the system directory, our OpenSSL should
automatically pick up the system managed certificates by default,
which seems like a useful property to have.

Author: indygreg

cpython-unix/build-openssl.sh

@@ -14,7 +14,14 @@ tar -xf openssl-${OPENSSL_VERSION}.tar.gz
 pushd openssl-${OPENSSL_VERSION}
 
 # Otherwise it gets set to /tools/deps/ssl by default.
-EXTRA_FLAGS="--openssldir=/etc/ssl"
+case "${TARGET_TRIPLE}" in
+    *apple*)
+        EXTRA_FLAGS="--openssldir=/private/etc/ssl"
+        ;;
+    *)
+        EXTRA_FLAGS="--openssldir=/etc/ssl"
+        ;;
+esac
 
 # musl is missing support for various primitives.
 # TODO disable secure memory is a bit scary. We should look into a proper