Link with gtk3 libs at link time. Normally gtklos would try to load them at
runtime but this wasn't working on macOS.
https://github.com/egallesio/STklos/issues/353#issuecomment-1465229597

Look only for goocanvas2, not goocanvas3. MacPorts doesn't have goocanvas3 yet
and I don't want this build to suddenly find and use goocanvas3 if it is added
to MacPorts in the future.
--- configure.orig	2023-03-12 11:10:11.000000000 -0500
+++ configure	2023-03-12 11:10:11.000000000 -0500
@@ -651,6 +651,7 @@
 LTLIBOBJS
 GOOVERS
 GOOCANV
+GTK_LIBS
 GTK_CFLAGS
 HAVE_CANVAS
 HAVE_GTK
@@ -7245,6 +7246,7 @@
 ## --- GTKLOS
 
 GTK_CFLAGS=""
+GTK_LIBS=""
 HAVE_GTK=0
 HAVE_CANVAS=0
 GOOCANV=absent
@@ -7254,11 +7256,12 @@
 if ${PKGCONFIG} --exists gtk+-3.0
 then
   GTK_CFLAGS=`${PKGCONFIG} --cflags gtk+-3.0`
+  GTK_LIBS=`${PKGCONFIG} --libs gtk+-3.0`
   HAVE_GTK=1
 fi
 
 # Do we have goocanvas?
-if ${PKGCONFIG} --exists goocanvas-3.0
+if false
 then
    GOOVERS=goocanvas-3.0
 else
@@ -7271,6 +7274,7 @@
 if test "X${GOOVERS}" != "X"
 then
    GTK_CFLAGS=`${PKGCONFIG} --cflags ${GOOVERS}`
+   GTK_LIBS=`${PKGCONFIG} --libs ${GOOVERS}`
    HAVE_GTK=1
    HAVE_CANVAS=1
    GOOCANV=present
--- extensions/gtklos/src/Makefile.in.orig	2021-11-24 07:45:27.000000000 -0600
+++ extensions/gtklos/src/Makefile.in	2023-03-12 11:12:06.000000000 -0500
@@ -203,6 +203,7 @@
 GOOCANV = @GOOCANV@
 GOOVERS = @GOOVERS@
 GTK_CFLAGS = @GTK_CFLAGS@
+GTK_LIBS = @GTK_LIBS@
 HAVE_CANVAS = @HAVE_CANVAS@
 HAVE_DLOPEN = @HAVE_DLOPEN@
 HAVE_GNOME = @HAVE_GNOME@
@@ -585,7 +586,7 @@
          $(GTKFLAGS) \
          -I$(BASEDIR)/src @GCINC@ @GMPINC@ \
          -c -o $*.o $*.c
-	@SH_LOADER@ @SH_LOAD_FLAGS@  $*.@SH_SUFFIX@ $*.o @DLLIBS@
+	@SH_LOADER@ @SH_LOAD_FLAGS@  $*.@SH_SUFFIX@ $*.o @DLLIBS@ $(GTK_LIBS)
 	/bin/rm -f $*.o
 
 $(EXTENSION)-incl.c: $(EXTENSION).stk $(SCM_SRCS)
--- extensions/gtklos/src/lib/libs.stk.orig	2021-09-29 03:34:58.000000000 -0500
+++ extensions/gtklos/src/lib/libs.stk	2023-03-12 11:10:11.000000000 -0500
@@ -35,8 +35,7 @@
 (when-load-and-compile
  (define *gtk-library-path*
    (append (build-path-from-shell-variable "STKLOS_GTK_DIR")
-           '("/usr/lib"          ;; Standard place
-             "/usr/local/lib"    ;; Standard place (also used by MacOS Homebrew)
+           '("@PREFIX@/lib"
              )))
 
  (define *gtk-library-suffix*