gnudatalanguage: fix build on older systems

Author: mohd-akram

math/gnudatalanguage/Portfile

@@ -99,7 +99,10 @@ variant wxWidgets description {Enable wxWidgets support} {
     configure.args-append   -DwxWidgets_CONFIG_EXECUTABLE=${wxWidgets.wxconfig}
 }
 
-default_variants            +wxWidgets
+# https://trac.macports.org/ticket/62087
+if {${os.platform} ne "darwin" || ${os.major} >= 16} {
+    default_variants        +wxWidgets
+}
 
 if {[gcc_variant_isset] || [clang_variant_isset]} {
     configure.args-replace  -DOPENMP=OFF \