rawtherapee: only default to +x11 if +quartz not set

See: https://github.com/macports/macports-ports/pull/23704
See: https://trac.macports.org/ticket/71173

graphics/rawtherapee/Portfile

@@ -170,17 +170,13 @@ if {${configure.build_arch} in [list ppc ppc64]} {
     # We do not want LTO on PowerPC builds.
     configure.args-append \
                         -DWITH_LTO=OFF
-
-#    default_variants-append \
-#                        +x11
-#} elseif {![variant_isset x11]} {
-#    default_variants-append \
-#                        +quartz
 }
 
 # +quartz requires non-default variants of its dependencies,
 # so it will be broken on buildbots.
-default_variants-append +x11
+if {![variant_isset quartz]} {
+    default_variants-append +x11
+}
 
 if {${configure.build_arch} ni [list i386 ppc ppc64] \
     && ![variant_isset quartz]} {