This commit rewrites our ancient `./configure` script from shell into Python.
The impetus for this change is to remove `config.mk` which is just a vestige of
the old makefile build system at this point. Instead all configuration is now
solely done through `config.toml`.
The python script allows us to more flexibly program (aka we can use loops
easily) and create a `config.toml` which is based off `config.toml.example`.
This way we can preserve comments and munge various values as we see fit.
It is intended that the configure script here is a drop-in replacement for the
previous configure script, no functional change is intended. Also note that the
rationale for this is also because our build system requires Python, so having a
python script a bit earlier shouldn't cause too many problems.
Closes#40730
This controls the value of the crt-static feature used when building the
standard library for a target, as well as the compiler itself when that
target is the host.
Some users of the build system change the git sha on every build due to
utilizing git to push changes to a remote server. This allows them to
simply configure that away instead of depending on custom patches to
rustbuild.
