The `--emit=llvm-ir` emits an optimized LLVM IR. For optimized builds it will be
highly inaccurate estimate of the amount IR generated initially.  While the
inaccuracy can be somewhat reduce after disabling the optimization, that in turn
has other unintended consequences, since opt-level controls the emission of
lifetime markers, sharing of generics between crates, instantiation of inline
functions, etc.

Use `-Csave-temps` and `no-opt` bitcode as a basis for more accurate estimate of
initial work handed of to the LLVM.

)

Document how to use WPA to profile rustc and what the normal workflow
should be for investigating bootstrap memory usage issues.

Co-authored-by: Ryan Levick <ryan.levick@gmail.com>

LLVM requires at least cmake 3.13.4.

https://www.llvm.org/docs/CMake.html

Co-authored-by: Camelid <camelidcamel@gmail.com>

* I-nominated are nominated for discussion

* Generalize meeting expression

Co-authored-by: Camelid <camelidcamel@gmail.com>

Co-authored-by: Camelid <camelidcamel@gmail.com>

Inspired by #1079. I used this command to find these typos:

    rg --multiline --pcre2 '\b([a-zA-Z]+) \1\b' src -tmd

There were a couple false positives of the form "that that" meaning
"that it" or "that this".