...which allows to align --enable/--disable switches on the part being en-/dis-
abled, as in

> --disable-assert-always-abort
>  --enable-avahi
>  --enable-breakpad
>  --enable-build-unowinreg
> --disable-ccache

for better readability

Change-Id: I490402c74ea1ee535deee6ef79274b588b614820
Reviewed-on: https://gerrit.libreoffice.org/48130Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>