According to Ossi the only safe characters in a path for qmake are
alphanumerical, underscore, dot and dash.

Task-number: QTCREATORBUG-10980
Change-Id: Ibacbfeb7f04f1f0524093f1d8fce637ea4ae6fd6
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>