This is a huge mess. Any windows executable does not understand
cygwin paths but for example the bash script only understands unix paths.

Additionally, os.path is unixpath so it is not able to correctly handle
windows paths. We therefore convert everything that we need to handle
to unix paths and only the few paths that are passed in the end to windows
executables back to the native format. We selected mixed mode
(windows path with forward slash) to allow the unix scripts to manipulate
paths.

Change-Id: Ic443415ff5e8277bf0bb8704bbafd35f50767288
Reviewed-on: https://gerrit.libreoffice.org/40755Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>