hg: build-infra/jdk9: Allow compilation with clang on linux.

[magnus.ihse.bursie at oracle.com]

Changeset: f201363d0ec9
Author:    ihse
Date:      2015-10-21 13:22 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/f201363d0ec9

Allow compilation with clang on linux.

! common/autoconf/flags.m4
! common/autoconf/generated-configure.sh