libnice: create ${S}/m4 directory before gtkdocize is called

* otherwise it fails with:
+ gtkdocize --docdir /OE/build/shr-core/tmp-eglibc/work/core2-64-oe-linux/libnice/0.0.13-r4/libnice-0.0.13
  ln: target 'm4/' is not a directory: No such file or directory
  cp: cannot create regular file 'm4/': Not a directory

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-oe/recipes-support/farsight/libnice_0.0.13.bb

@@ -23,6 +23,10 @@ FILES_${PN}-dev += "${libdir}/gstreamer-0.10/*.la"
 FILES_${PN}-staticdev += "${libdir}/gstreamer-0.10/*.a"
 FILES_${PN}-dbg += "${libdir}/gstreamer-0.10/.debug"
 
+do_configure_prepend() {
+    mkdir ${S}/m4 || true
+}
+
 do_compile_append() {
     for i in $(find ${S} -name "*.pc") ; do
         sed -i -e s:${STAGING_DIR_TARGET}::g \