Bug#763909: Bug#767919: unblock: viewmol/2.4.1-21

[Graham Inggs]

Some progress.

I pre-applied debian/patches/150-getmachine_multiarch.patch simply by 
running:

$ patch -p 1 -i debian/patches/150-getmachine_multiarch.patch

...and then commented out the line:

#150-getmachine_multiarch.patch

..from debian/patches/series.  I uploaded this to the Ubuntu PPA 
builders for Vivid, Utopic and Trusty.
Some architectures built /usr/bin/viewmol and others didn't, seemingly 
at random.
Comparing the buildlogs, I found those that ran:

debian/rules clean
debian/rules build
debian/rules binary

...built the executable, whereas those that ran:

debian/rules clean
debian/rules build-arch
debian/rules binary-arch

...did not.  I should be able to figure this out now.