build: Use newest config.{guess,sub} available

Author: hebasto

autogen.sh

@@ -14,3 +14,12 @@ fi
 command -v autoreconf >/dev/null || \
   (echo "configuration failed, please install autoconf first" && exit 1)
 autoreconf --install --force --warnings=all
+
+if expr "'$(build-aux/config.guess --timestamp)" \< "'$(depends/config.guess --timestamp)" > /dev/null; then
+  cp depends/config.guess build-aux
+  cp depends/config.guess src/secp256k1/build-aux
+fi
+if expr "'$(build-aux/config.sub --timestamp)" \< "'$(depends/config.sub --timestamp)" > /dev/null; then
+  cp depends/config.sub build-aux
+  cp depends/config.sub src/secp256k1/build-aux
+fi