[dev.cc] cmd/8g: work around "out of fixed registers" on Plan 9
This change works around the "out of fixed registers"
issue with the Plan 9 C compiler on 386, introduced by
the Bits change to uint64 in CL
169060043.
The purpose of this CL is to be able to properly
follow the conversion of the Plan 9 runtime to Go
on the Plan 9 builders.
This CL could be reverted once the Go compilers will
be converted to Go.
Thanks to Nick Owens for investigating this issue.
LGTM=rsc
R=rsc
CC=austin, golang-codereviews, mischief
https://golang.org/cl/
177860043