build: Add a release script

I've goofed up too many times producing the separate
doc tarballs. So lets collect the required steps in a script.

make-release.sh

@@ -0,0 +1,30 @@
+#! /bin/sh
+
+version=$(head -5 meson.build | grep version | sed -e "s/[^']*'//" -e "s/'.*$//")
+release_build_dir="release_build"
+branch=$(git branch --show-current)
+
+if [ -d ${release_build_dir} ]; then
+  echo "Please remove ./${release_build_dir} first"
+  exit 1
+fi
+
+# we include gtk-doc since we need the gtk-doc-for-gtk4 branch
+meson setup --force-fallback-for gtk-doc ${release_build_dir} || exit
+
+# make the release tarball
+meson dist -C${release_build_dir} --include-subprojects || exit
+
+# now build the docs
+meson configure -Dgtk_doc=true ${release_build_dir} || exit
+ninja -C${release_build_dir} gdk4-doc gsk4-doc gtk4-doc || exit
+
+tar cf ${release_build_dir}/meson-dist/gdk-docs-${version}.tar.xz ${release_build_dir}/docs/reference/gdk
+tar cf ${release_build_dir}/meson-dist/gsk-docs-${version}.tar.xz ${release_build_dir}/docs/reference/gsk
+tar cf ${release_build_dir}/meson-dist/gtk-docs-${version}.tar.xz ${release_build_dir}/docs/reference/gtk
+
+echo -e "\n\nGTK ${version} release on branch ${branch} in ./${release_build_dir}/:\n"
+
+ls -l --sort=time -r "${release_build_dir}/meson-dist"
+
+echo -e "\nPlease sanity-check these tarballs before uploading them."