installer: Set the working directory when running mingw-get

This allows to use paths relative to the installation directory in package
post-install Lua code when running mingw-get as part of the installation.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Revert "installer: Set the working directory when running mingw-get"

This reverts commit eb499c7 because being in mingw/bin simplifies calling
git in the post-install action.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Add msys-automake and msys-libtool as required packages

Building MSYS packages is better done with the MSYS build tools instead of
fall back to the corresponding MinGW build tools.

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Merge branch 'master' of https://github.com/sschuberth/mingwGitDevEnv