Add libtool 2.4.7

Instead of using the pre-generated "bootstrap" script, execute the
relevant bootstrap operations manually. This doesn't actually change
the build output; the final package hash remains identical.

sysc/libtool-2.4.7/import-gnulib.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+# SPDX-FileCopyrightText: 2022 Dor Askayo <dor.askayo@gmail.com>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set -e
+
+../gnulib-a521820/gnulib-tool \
+    --no-changelog \
+    --avoid=dummy \
+    --libtool \
+    --macro-prefix=GL \
+    --with-tests \
+    --tests-base=gnulib-tests \
+    --aux-dir=build-aux \
+    --m4-base=m4 \
+    --local-dir=gl \
+    --local-dir=gl-mod/bootstrap \
+    --symlink \
+    --import announce-gen \
+        bootstrap \
+        do-release-commit-and-tag \
+        extract-trace \
+        gendocs \
+        git-version-gen \
+        gitlog-to-changelog \
+        gnu-web-doc-update \
+        gnupload \
+        inline-source \
+        maintainer-makefile \
+        options-parser \
+        readme-release \
+        update-copyright