BSD find puts in extra slashes if you leave a trailing slash in the argument

this breaks just below when we use cut on /

Author: embray

bootstrap

@@ -31,7 +31,7 @@ CONFVERSION=`cat $PKG/package-version.txt`
 bootstrap () {
     rm -f m4/sage_spkg_configures.m4
     spkg_configures=""
-    for filename in $(find build/pkgs/ -type f -name spkg-configure.m4); do
+    for filename in $(find build/pkgs -type f -name spkg-configure.m4); do
         pkgname="$(echo $filename | cut -d/ -f3)"
         echo "m4_sinclude([$filename])" >> m4/sage_spkg_configures.m4
         spkg_configures="$spkg_configures