libtool: Make sure ltmain.sh is always regenerated. We can't just remove it since it has to be present to run configure

meta/packages/libtool/libtool_2.2.6.bb

@@ -1,6 +1,6 @@
 require libtool.inc
 
-PR = "r20"
+PR = "r21"
 
 SRC_URI = "${GNU_MIRROR}/libtool/libtool-${PV}a.tar.gz \
            file://trailingslash.patch;patch=1 \
@@ -16,6 +16,12 @@ inherit autotools
 
 EXTRA_AUTORECONF = "--exclude=libtoolize"
 
+do_compile_prepend () {
+	# Sometimes this file doesn't get rebuilt, force the issue
+	rm -f ${S}/libltdl/config/ltmain.sh
+	make libltdl/config/ltmain.sh
+}
+
 #
 # We want the results of libtool-cross preserved - don't stage anything ourselves.
 #