Fix inconsistency.

Fix inconsistency.

On linux, pkg-config.py outputs a 4-tuple. The non-linux fallback path
outputs only a 3-tuble, which confuses pkg_config.gni.

BUG=none
R=brettw@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=242456

[Nico, 2013-12-24 18:51:14]

Not sure why this fallback path is here at all though, I'd just remove it and
make it a hard error if this script gets called on non-linux.

[brettw, 2013-12-24 21:15:24]

LGTM.

Scottmg and I were hoping to make builds of another platform have some kind of
default behavior so one can test what effects a change has on flags and such on
any platform. That surely doesn't work now and it might be a losing battle, but
it still seems desirable.

[Nico, 2013-12-24 21:45:07]

Committed patchset #1 manually as r242456.