x86_64 is used as a baseline: the "x86_64" entry, whatever status it has,
is transformed into "all", and then the other entries in ARCHITECTURES
either dropped or rearranged appropriately.
In GCC5 the preprocessor changed the format of its line number output,
breaking the alien_svn build. Until this is fixed upstream, work around
the issue by disabling preprocessor line numbering.
The absence of alien_svn made the git_svn subpackage uninstallable on
x86_64.
See "Preprocessor issues" in: https://gcc.gnu.org/gcc-5/porting_to.html
* Referring the current haiku version explicitly is not needed, since
the RequiresUpdater takes care of setting the version of Haiku used
for building a package.
