--- Portfile.orig	2012-11-01 08:16:02.000000000 +0100
+++ Portfile	2012-11-01 17:43:13.000000000 +0100
@@ -150,6 +150,15 @@
 configure.universal_args-delete --disable-dependency-tracking
 
 if {[variant_isset universal]} {
+    # the following is inspired by the icu Portfile
+    # if we can't run executables for the target arch, mark it as a cross-compile
+    foreach arch ${configure.universal_archs} {
+        if {((${os.major} < 9 || [sysctl hw.cpu64bit_capable] == 0) && ($arch == "x86_64" || $arch == "ppc64")) 
+            || (${os.arch} == "powerpc" && ($arch == "x86_64" || $arch == "i386"))
+            || (${os.arch} == "i386" && ($arch == "ppc" || $arch == "ppc64"))} {
+            set merger_configure_args($arch) "--enable-cross-compile --target-os=${os.platform}"
+        }
+    }
     foreach arch ${configure.universal_archs} {
         set merger_host($arch) ""
         lappend merger_configure_args($arch) --arch=${arch}