Cleaner than deciding on startup with an env variable

Having ninja in the PATH should be good enough.
If that didn't work, we try to find it in the most logical location
relative to CHROMIUM_SRC_DIR and bail out otherwise.
Since it seems unlikely to vary, and can be convenient to keep persistent,
we put it in .qmake.cache if qmake uses a cache.

process uses the same code as lib and decides at runtime which
code to run. Fix the debug build by making sure that all infrastructure
code is available in both process and lib by building common code
not shared directly through chromium sources in a separate static lib.

Change the semantics of getOutDir, introduce getConfigDir.
Rely on Gyp's configurations mechanism to get a sensible
path for the BLINQ_PROCESS_PATH in both cases.
Also make the build smarter in that re-generation of gyp files
will lead to re-gyping.

This should allow us to have much better integration by generating the necessary gyp
files directly from qmake.
Mostly works for now, though we will most likely need to build the gyp generation
as we go.

  * Out dir logic is still crap and needs to be (re)worked.
  * In the same vein, we probably don't want the generated gyp
  content ending up in the source tree in the long run, which could prove tricky
  with relative paths to sources and all.

We'll probably add a qmake wrapper for it later, but for now that should do.