config: add pigz to build_packages (MR 2561)

Speed up compressing packages after build by using pigz which does
parallelised compression!

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

pmb/config/__init__.py

@@ -222,7 +222,7 @@ chroot_outdated = 3600 * 24 * 2
 # NOTE: full hexdump is installed to workaround a bug in busybox,
 # see https://gitlab.postmarketos.org/postmarketOS/pmaports/-/issues/3268. This can be
 # reverted when the bug is properly fixed.
-build_packages = ["abuild", "apk-tools", "build-base", "ccache", "git", "hexdump"]
+build_packages = ["abuild", "apk-tools", "build-base", "ccache", "git", "hexdump", "pigz"]
 
 #
 # PARSE