build panic on ppc

[frank6600]

As title, build whill panic on ppc,
Option::unwrap() on a None value, build.rs:358:10

[he32]

This is rings way of telling you "not implemented for this platform".
I have the same itch, as bulk pkgsrc builder for NetBSD/powerpc, and I see an increasing number of rust packages fail to build due to the vendored inclusion of this module.
The list of supported platforms can be found around line 216 in build.rs in the ASM_TARGETS table.

...and, issue #1555 is fairly strongly related to this.

[briansmith]

Closing this as a duplicate of an earlier PPC issue.