Barnes: Parallel ./configure

Tavian Barnes takes onthe tedious process of waiting for configure scripts to run.

I paid good money for my 24 CPU cores, but ./configure can onlymanage to use 69% of one of them. As a result, this random projecttakes about 13.5* longer to configure the build than it does toactually do the build.

The purpose of a ./configure script is basically to run thecompiler a bunch of times and check which runs succeeded. In thisway it can test whether particular headers, functions, structfields, etc. exist, which lets people write portable software. Thisis an embarrassingly parallel problem, but Autoconf can'tparallelize it, and neither can CMake, neither can Meson, etc.,etc.

(Thanks to Paul Wise).