gbuild-to-ide: Make it work for GNU make 4.x

Since GNU make 4.0 the output of --print-data-base command has been
slightly changed, so that class specific attributed aren'tt prefixed
with "#" char any more. To prevent the duplication of used regexs or
discontinuation of supporting widely used GNU make version 3.8x detect
the case that matches this regex:

target : VAR := VALUE

pand repend '#' character to retry the match for "pseudo" hash-starting
line. This way the same script works for both worlds.

Test Plan:

* have full build of LibreOffice
* install GNU make 4
* verify that gbuild-to-ide is able to parse and emit sane debug project
  configuration for both GNU make versions:
  $ make-3.8 debug-ide-integration
  $ make-4 debug-ide-integration

Change-Id: I7d760d9570f2df510571cc1e8fd7f31115d43b92
Reviewed-on: https://gerrit.libreoffice.org/11751
Tested-by: Peter Foley <pefoley2@verizon.net>
Reviewed-by: Peter Foley <pefoley2@verizon.net>