Make it easier to specify a qmake executable inside a docker device

Right now you depend on the docker plugin finding the right qmake executable.

In Debian packages you have platform specific names for the qmake executable (example: arm-linux-gnueabihf-qmake). It's actually a wrapper which sets up some things for cross-compilation.

That executable/wrapper is not found by the docker plugin. I would like to add it manually, but the only way now is by editing a file.

There are some options here I think:

• Allow the user to specify custom names for the qmake executable when searching for qmake binaries automatically. (So the plugin would search for the names given by the user)
• Allow the user to easily add a path to qmake manually (without needing to edit config files)
• This might be too specific to certain implementations, but maybe the plugin could search for qmake executables with platform specific names, like it already does with cross-compilers.