coreboot-toolchain: Introduce script for generating sources file

Add and adjust update script from
https://git.petabyte.dev/petabyteboy/corenix.

The script is meant to be run from the package directory of the
coreboot-toolchain. The script generates a sources.nix files, which
contains all sources used for the coreboot toolchain and some other
tools. Thus, it needs to be stripped down to the necessary sources.

Signed-off-by: Felix Singer <felixsinger@posteo.net>

pkgs/development/tools/misc/coreboot-toolchain/update.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env nix-shell
+#!nix-shell --pure -i bash -p nix cacert git getopt
+
+rootdir="../../../../../"
+
+src="$(nix-build $rootdir --no-out-link -A coreboot-toolchain.src)"
+urls=$($src/util/crossgcc/buildgcc -u)
+
+tmp=$(mktemp)
+echo '{ fetchurl }: [' > $tmp
+
+for url in $urls; do
+  name="$(basename $url)"
+  hash="$(nix-prefetch-url "$url")"
+
+  cat << EOF >> $tmp
+  {
+    name = "$name";
+    archive = fetchurl {
+      sha256 = "$hash";
+      url = "$url";
+    };
+  }
+EOF
+done
+
+echo ']' >> $tmp
+
+sed -ie 's/https\:\/\/ftpmirror\.gnu\.org/mirror\:\/\/gnu/g' $tmp
+
+mv $tmp sources.nix