Fix zero build on arm

[Omair Majid]

Hi,

The following webrev makes zero build succesfully on arm:
http://cr.openjdk.java.net/~omajid/webrevs/zero-on-arm/00/

The only problem I ran into while trying to build zero on armv7l is that
the gcc there does not like -m32. The changes make the build system
check whether the compiler supports the -m32/-m64 flag before using it.

Any thoughts or comments?

Thanks,
Omair

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