Index: tk/build.sh
==================================================================
--- tk/build.sh
+++ tk/build.sh
@@ -147,10 +147,16 @@
 			(
 				. "${patchscript}"
 			)
 		fi
 	done
+
+	# Allow wrapper programs to supplant real programs
+	if [ -d 'fake-bin' ]; then
+		PATH="$(pwd)/fake-bin:${PATH}"
+		export PATH
+	fi
 
 	for dir in "${TCLCONFIGDIRTAIL}" unix win macosx win64 __fail__; do
 		if [ -z "${dir}" ]; then
 			continue
 		fi

ADDED   tk/patchscripts/xmkmf-donotuse.sh
Index: tk/patchscripts/xmkmf-donotuse.sh
==================================================================
--- /dev/null
+++ tk/patchscripts/xmkmf-donotuse.sh
@@ -0,0 +1,24 @@
+#! /bin/bash
+
+# If we are not cross-compiling then don't worry about replacing "xmkmf" with a wrapper
+if [ -z "${CC}" ]; then
+	exit 0
+fi
+
+case "$(basename "${CC}")" in
+	*-*-*)
+		;;
+	*)
+		exit 0
+esac
+
+# Create an "xmkmf" wrapper which exits in failure so that autoconf will try
+# to locate headers/libraries normally
+mkdir fake-bin >/dev/null 2>/dev/null
+
+cat << \_EOF_ > fake-bin/xmkmf
+#! /bin/bash
+exit 1
+_EOF_
+
+chmod +x fake-bin/xmkmf