Rename the CAfile to cert.pem since that's the hardcoded default.

$ strings ~/.rbenv/versions/2.0.0-rc2/openssl/lib/libcrypto.a |
  grep -B3 SSL_CERT_FILE
/Users/jeremy/.rbenv/versions/2.0.0-rc2/openssl/ssl/certs
/Users/jeremy/.rbenv/versions/2.0.0-rc2/openssl/ssl/cert.pem
SSL_CERT_DIR
SSL_CERT_FILE

bin/ruby-build

@@ -558,7 +558,7 @@ build_package_mac_openssl() {
   build_package_standard "$@"
 
   # Extract root certs from the system keychain in .pem format and rehash.
-  local pem_file="$OPENSSLDIR/cacert.pem"
+  local pem_file="$OPENSSLDIR/cert.pem"
   security find-certificate -a -p /Library/Keychains/System.keychain > "$pem_file"
   security find-certificate -a -p /System/Library/Keychains/SystemRootCertificates.keychain >> "$pem_file"
   "$OPENSSL_PREFIX_PATH/bin/c_rehash" "$OPENSSLDIR" >&4 2>&1