Bug#708285: morse-simulator: FTBFS when not building -doc package

[Aaron M. Ucko]

Source: morse-simulator
Version: 1.0.1-1
Severity: serious
Justification: fails to build from source

Builds of morse-simulator only covering its architecture-dependent
binary packages (as on the autobuilders) have been failing:

  cd /.../morse-simulator-1.0.1/debian/morse-simulator-doc/usr/share/doc/morse/html/_static/ && rm -f jquery.js underscore.js && ln -s /usr/share/javascript/jquery/jquery.js && ln -s /usr/share/javascript/jquery/underscore.js
  /bin/sh: 1: cd: can't cd to /.../morse-simulator-1.0.1/debian/morse-simulator-doc/usr/share/doc/morse/html/_static/
  make[1]: *** [override_dh_install] Error 2

Could you please arrange to run those commands only when actually
building the architecture-independent morse-simulator-doc package?
I'd also suggest cleaning up the unnecessary use of $(PWD) while
you're at it, but that's no big deal.

Thanks!