sync autogen.sh with LibreSSL, cache upstream config scripts

autogen.sh

@@ -5,6 +5,12 @@ set -e
 mkdir -p m4
 rm -fr autom4te.cache
 autoreconf -i
-chmod -R u+w .
-curl 'http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD' > config.guess
-curl 'http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD' > config.sub
+
+# Patch libtool 2.4.2 to pass -fstack-protector as a linker argument
+sed 's/-fuse-linker-plugin)/-fuse-linker-plugin|-fstack-protector*)/' \
+  ltmain.sh > ltmain.sh.fixed
+mv -f ltmain.sh.fixed ltmain.sh
+
+# Update config scripts and fixup permissions
+find . ! -perm -u=w -exec chmod u+w {} \;
+cp scripts/config.* .