hg: jdk/sandbox: 8210283: Support git as an SCM alternative in the build

[chris.hegarty at oracle.com]

Changeset: 5a1be00ea4f6
Author:    erikj
Date:      2018-09-07 14:54 -0700
URL:       http://hg.openjdk.java.net/jdk/sandbox/rev/5a1be00ea4f6

8210283: Support git as an SCM alternative in the build
Reviewed-by: ihse, ehelin

+ .gitignore
! make/SourceRevision.gmk
! make/autoconf/basics.m4
! make/autoconf/spec.gmk.in
! make/common/MakeBase.gmk