hg: build-infra/jdk9/hotspot: Fix merge problem: DEBUG_SYMBOL := true has no meaning anymore, nor is it required.

[magnus.ihse.bursie at oracle.com]

Changeset: 4b3fe9918a70
Author:    ihse
Date:      2016-01-29 15:59 +0100
URL:       http://hg.openjdk.java.net/build-infra/jdk9/hotspot/rev/4b3fe9918a70

Fix merge problem: DEBUG_SYMBOL := true has no meaning anymore, nor is it required.

! makefiles/lib/CompileDtrace.gmk
! makefiles/lib/CompileJvm.gmk
! makefiles/lib/CompileLibjsig.gmk