Capture libeigen's header correctly

libeigen exports entire directory, but only two directories contain
actual exported headers. And some of headers have no extension. This
adds a special behaviour for external/eigen when capturing snapshot.

Exempt-From-Owner-Approval: trivial comment change

Bug: 157106227
Test: m vendor-snapshot captures libeigen's headers
Change-Id: I47830c8818a7fe804c8a769069804275b09e99e8
1 file changed