Builds for all mips* platforms, using the zero backend. A mips port
properly is in process but has been "getting close to ready" for years
now, so we are using the much more tested zero backend.
mipshf had a branch jump error (mips hates super large branch jumps).
This is a known bug that is not going to be fixed very easily. To
workaround this, I reduced the jump by ~400 lines of assembly by
compiling with -Os, enough to make the jump close enough.
[ci skip]
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