Change test for being in build-webos

meta-openembedded may not be present in other distros, so check for
Makefile.in instead

Open-webOS-DCO-1.0-Signed-off-by: Keith Derrick <keith.derrick@palm.com>

Change-Id: Ide46ca4267954e099dfd7c4239848a42fa1764e2
Reviewed-on: http://g2g.palm.com/1392
Reviewed-by: Keith Derrick <keith.derrick@palm.com>
Tested-by: Keith Derrick <keith.derrick@palm.com>