Use brew --prefix to get brew package config path for install script

[dsherret]

We noticed the Bun package manager is excluding the install script for your package because it is slow.

https://github.com/oven-sh/bun/blob/a305e99af5d9dbe74ffabfa5a3c0cfdf815ac71a/src/install/postinstall_optimizer.zig#L14-L19

In Deno we were looking into making a similar optimization, but we don't believe it would be good to override your preferences just so we can do better on an install benchmark.

I was looking at the code and I believe that it should actually get the value from brew --prefix then ./lib/pkgconfig. I'm not sure though. It is much faster to do this on my machine.

% hyperfine --warmup 5 "brew --prefix" "brew environment --plain"
Benchmark 1: brew --prefix
  Time (mean ± σ):      22.9 ms ±   1.6 ms    [User: 8.3 ms, System: 8.8 ms]
  Range (min … max):    18.8 ms …  29.1 ms    120 runs
 
Benchmark 2: brew environment --plain
  Time (mean ± σ):     789.2 ms ±  65.3 ms    [User: 209.1 ms, System: 139.0 ms]
  Range (min … max):   714.9 ms … 884.1 ms    10 runs
 
Summary
  brew --prefix ran
   34.41 ± 3.68 times faster than brew environment --plain

[lovell]

Hi David, thank you for taking the time to investigate the problem and provide a solution, this will definitely improve things for those using Homebrew and building from source .

Luckily this class of problem should disappear in the next release as build from source becomes opt-in, please see #4490 (comment) for more details.