RFR(M): 8046471: Use OPENJDK_TARGET_CPU_ARCH instead of legacy value for hotspot ARCH

[Mikael Vidstedt]

All,

I need some feedback and comments on the below fix:

Bug: https://bugs.openjdk.java.net/browse/JDK-8046471
Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8046471/webrev.00/webrev/

Background:

When configuring the hotspot build the build system sets up the ARCH 
variable to reflect the target cpu. Currently the value is initialized 
to OPENJDK_TARGET_CPU_LEGACY, which is the internal legacy cpu name. For 
example, on x86 64-bit this is amd64 on linux (but x86_64 on mac). The 
goal in the new (JDK) build system is to have the "legacy" value 
gradually removed in favor of the other variables.

Discussion:

The two candidate variables to base ARCH on are as far as I can tell 
OPENJDK_TARGET_CPU and OPENJDK_TARGET_CPU_ARCH. Of the two 
OPENJDK_TARGET_CPU_ARCH is the more "stable" one, with a single, well 
defined value per cpu family { arm, ppc, s390, sparc, x86 }. Together 
with ARCH_DATA_MODEL/LP64 that information should be enough for the 
Hotspot build system to do its thing. Note: ARCH is currently ignored on 
solaris and bsd - it's overridden at the top of the respective 
make/<os>/makefiles/defs.make files.

Before I go too far with this though I'd like to get some feedback on 
whether or not this is the right approach and what the exact value 
should be. Depending on the outcome of that the Hotspot build system may 
have to be updated for some platforms to support the new value(s).

Thanks,
Mikael