full changelog at https://blog.rust-lang.org/2017/11/22/Rust-1.22.html
port changes:
- switch to clang and libc++ (instead of egcc and estdc++)
- use devel/llvm instead of the embedded llvm version
- make i386 produce code for 'pentiumpro' instead of 'pentium4' so that
ppl can use ripgrep on pentium II's (yay!)
- use a hack (codegen-units=16) to fix memory pressure issues on i386.
Might not work forever.....
tested on i386 & amd64, went into an i386 bulk.
all the hard work from semarie@