RFR: JDK-8204602 Add devkit for linux-arm32

Fri Jun 8 08:38:44 UTC 2018

With some simple changes, our devkit scripts can be made to generate 
devkits for cross-compiling on linux-x64 to linux-arm (32-bit). Also add 
a jib profile to use this new linux-arm devkit, as opposed to the legacy 
devkits used by the traditional linux-arm profiles.

Note that this change does not imply any change in Oracle's support of 
the linux-arm platform.

Bug: https://bugs.openjdk.java.net/browse/JDK-8204602
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8204602-add-linux-arm-32-devkit/webrev.01

/Magnus