apr: Split into multiple outputs

This is important because apr stores a copy of libtool, which in turn
contains a reference to GCC.

pkgs/development/libraries/apr-util/default.nix

@@ -19,11 +19,13 @@ stdenv.mkDerivation rec {
   configureFlags = ''
     --with-apr=${apr} --with-expat=${expat}
     --with-crypto
-    ${stdenv.lib.optionalString sslSupport "--with-openssl=${openssl}"}
+    ${stdenv.lib.optionalString sslSupport "--with-openssl"}
     ${stdenv.lib.optionalString bdbSupport "--with-berkeley-db=${db4}"}
     ${stdenv.lib.optionalString ldapSupport "--with-ldap"}
   '';
 
+  buildInputs = stdenv.lib.optional sslSupport openssl;
+
   propagatedBuildInputs = stdenv.lib.optional ldapSupport openldap;
 
   enableParallelBuilding = true;