svn-proto: use export to clone the build directory

Cut back on the clone size by skipping the .svn working directories.
Contrary to FS#28697 which requested this, the removal of the original
build directory will stay, to ensure that there are no problems as a
result of a dirty build directory.
Signed-off-by: Dave Reisner <dreisner@archlinux.org>

prototypes/PKGBUILD-svn.proto

@@ -44,7 +44,7 @@ build() {
   msg "Starting build..."
 
   rm -rf "$srcdir/$_svnmod-build"
-  cp -r "$srcdir/$_svnmod" "$srcdir/$_svnmod-build"
+  svn export "$srcdir/$_svnmod" "$srcdir/$_svnmod-build"
   cd "$srcdir/$_svnmod-build"
 
   #