Updating dpkg-buildflags to enable reproducible=+fixfilepath by default

[Sune Vuorela]

On 2020-11-13, Vagrant Cascadian <vagrant at reproducible-builds.org> wrote:
> If it could be fixed at the core for QFINDTESTDATA, that would be nicer
> than fixing 20-30 packages individually, though we're not there right
> now.

Unfortunately, only like 10% of the relevant packages have test suites
enabled and run, because gettings things to work reliable is sometimes
hard.
Adding more hurdles does not help. 
I think this is a hurdle we do not need.

/Sune