GFFI build system does not detect grep errors

[GoogleCodeExporter]

When we parse the system headers, sometimes grep will fail (e.g. Apple's grep 
on current versions of Lion).

This causes empty files to be emitted and compiled, eventually causing failures 
in GFFI libraries like fs-base at run time, because constants cannot be 
resolved.

We need to detect this failure and abort the build, so that users know to 
upgrade their version of grep to a more capable one.

Original issue reported on code.google.com by wes@page.ca on 5 Oct 2011 at 12:20

[GoogleCodeExporter]

Original comment by wes@page.ca on 9 Oct 2011 at 11:12

• Added labels: Milestone-Release0.2, Priority-Critical
• Removed labels: Priority-Medium