hg: build-infra/jdk9/hotspot: * Better design of JvmPlatforms to allow setup of TARGET_OS_ARCH_os_cpu flags properly.

[magnus.ihse.bursie at oracle.com]

Changeset: 9ac603d61b5c
Author:    ihse
Date:      2015-10-07 13:50 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk9/hotspot/rev/9ac603d61b5c

* Better design of JvmPlatforms to allow setup of TARGET_OS_ARCH_os_cpu flags properly.
* Rename OS_SUBDIR to HOTSPOT_OS_TARGET.
* Start implementing proper dtrace support.

! makefiles/Common.gmk
! makefiles/CompileJvm.gmk
! makefiles/JvmFeatures.gmk
! makefiles/JvmPlatforms.gmk