gcam: Fix macOS 11+ libtool bug

cad/gcam/Portfile

@@ -33,4 +33,5 @@ depends_build   port:pkgconfig
 depends_lib     port:gtkglext \
                 port:libpng
 
-patchfiles      libpng-1.5.patch
+patchfiles      dynamic_lookup-11.patch \
+                libpng-1.5.patch

cad/gcam/files/dynamic_lookup-11.patch

@@ -0,0 +1,25 @@
+Recognize macOS 11 and later, remove inaccurate comment, and simplify.
+https://debbugs.gnu.org/cgi/bugreport.cgi?bug=44605
+--- configure.orig	2010-07-27 14:19:00.000000000 -0500
++++ configure	2023-07-21 01:11:09.000000000 -0500
+@@ -6353,16 +6353,11 @@
+       _lt_dar_allow_undefined='${wl}-undefined ${wl}suppress' ;;
+     darwin1.*)
+       _lt_dar_allow_undefined='${wl}-flat_namespace ${wl}-undefined ${wl}suppress' ;;
+-    darwin*) # darwin 5.x on
+-      # if running on 10.5 or later, the deployment target defaults
+-      # to the OS version, if on x86, and 10.4, the deployment
+-      # target defaults to 10.4. Don't you love it?
+-      case ${MACOSX_DEPLOYMENT_TARGET-10.0},$host in
+-	10.0,*86*-darwin8*|10.0,*-darwin[91]*)
+-	  _lt_dar_allow_undefined='${wl}-undefined ${wl}dynamic_lookup' ;;
+-	10.[012]*)
++    darwin*)
++      case ${MACOSX_DEPLOYMENT_TARGET},$host in
++	10.[012],*|,*powerpc*-darwin[5-8]*)
+ 	  _lt_dar_allow_undefined='${wl}-flat_namespace ${wl}-undefined ${wl}suppress' ;;
+-	10.*)
++	*)
+ 	  _lt_dar_allow_undefined='${wl}-undefined ${wl}dynamic_lookup' ;;
+       esac
+     ;;