hg: build-infra/jdk9: Generalize handling of native file extensions.

[magnus.ihse.bursie at oracle.com]

Changeset: 128a57e3da40
Author:    ihse
Date:      2014-11-25 13:01 +0100
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/128a57e3da40

Generalize handling of native file extensions.

! common/autoconf/spec.gmk.in
! make/common/NativeCompilation.gmk