This switches the defaults to ensure that everything is built with the build
compiler rather than the host compiler itself (which we're not guaranteed to be
able to run)
This commit fixes a longstanding issue with the makefiles where all host
platforms bootstrap themselves. This commit alters the build logic for the
bootstrap to instead only bootstrap the build triple, and all other compilers
are compiled from that one compiler.
The benefit of this change is that we can cross-compile compilers which cannot
run on the build platform. For example our builders could start creating
`arm-unknown-linux-gnueabihf` compilers.
This reduces the amount of bootstrapping we do, reducing the amount of test
coverage, but overall it should largely just end in faster build times for
multi-host compiles as well as enabling a feature which can't be done today.
cc #5258
This commit is the start of a series of commits which start to replace the
makefiles with a Cargo-based build system. The aim is not to remove the
makefiles entirely just yet but rather just replace the portions that invoke the
compiler to do the bootstrap. This commit specifically adds enough support to
perform the bootstrap (and all the cross compilation within) along with
generating documentation.
More commits will follow up in this series to actually wire up the makefiles to
call this build system, so stay tuned!
