unfs-server: Fix do_configure so it can be re-executed safely

[YOCTO #2194]

(From OE-Core rev: 43e6fec78e36beb770fd47b0c4631d7382025d6b)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/unfs-server/unfs-server_2.1+2.2beta47.bb

@@ -62,7 +62,9 @@ do_configure_prepend () {
     # 64-bit architectures:
     rm -f *_xdr.c
 
-    mv aclocal.m4 acinclude.m4
+    if [ ! -f ${S}/acinclude.m4 ]; then
+        mv ${S}/aclocal.m4 ${S}/acinclude.m4
+    fi
 }
 
 # This recipe is intended for -native and -nativesdk builds only,