This was originally reported by Matthias Klose:

The attached patch adds support for building zero for the x86_64-linux-gnux32
target, having changes in the build system, hotspot and jdk.

 - the build system currently only derives the target from
   the cpu in PLATFORM_EXTRACT_VARS_FROM_CPU; that is not enough
   for the new target, which only differs by the ending of the
   triplet. However the $host macro should be available anywhere.

 - the hotspot part just handles the new "cpu"

 - GensrcX11Wrappers.gmk assumes that there is a black/white
   decision about -m32/-m64. The patch works around it. However
   the real patch should be to get these flags from the build
   system, and not hardcode itself.

 - the sysctl system call is unsupported in the x32 kernel, and
   just the include leads to a build error. From my point of view
   the header is not needed. I had successful builds on all other
   targets without including it. If you want to keep the include,
   then it should be guarded with
   #if !(defined(_ILP32) && defined(__x86_64__))

Matthias