Add target to remove the subdirectory including the version number (or
date) from the output directory. The output directory can be selected
with the --output-dir option.

This should have been added with commit 5846dfae.

This will allow sharing more containers between components, where the
default list of packages is enough.

Add the old OSX toolchain based on gcc rather than clang.

This is building for Linux and Windows, but not yet for OSX.

Copy get-moz-build-date from builders/tor-browser-bundle.git.

Install hardening-wrapper, since the compiler setup on Linux requires
it.

Use #!/bin/bash rather than #!/bin/sh in the build scripts since the
compiler setup use bash specific commands.