Publish host builds of mips, mipsel, mips64el for Linux

[brson]

Today we publish target builds for mips and mipsel, and have no support for mips64el. All three of these are or will soon be supported by Debian and Fedora.

• mips
• mipsel
• mips64el

cc #36006 (comment)

[japaric]

mips64el

#36024 adds the target definition to the compiler.

[japaric]

I managed to produce functional rustcs for the mips and mipsel targets. I've sent the required changes to the rust-buildbot repository (rust-lang-deprecated/rust-buildbot#121).

[alexcrichton]

Just deployed a change for mips/mipsel, we should hopefully have those tomorrow night

[alexcrichton]

Ok, added mips64 as well, closing.

[alexcrichton]

Complications last night prevented these nightlies from going out, hopefully tonight though!