Auto merge of #24051 - TheGoddessInari:fix_windows, r=jdm

build_commands: Make Visual Studio detection not assume environment

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Ever since 681d7b165a849bc2c93b11b5968d345f1868a987, servo breaks building if you're not running Visual Studio 2015 or 2017 in the default location on C:.

I rewrote the PR to not assume environment, similarly to #23098.

We need to stop meeting like this. 🦊

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because 681d7b165a849bc2c93b11b5968d345f1868a987 didn't. Realistically, there should be environment tests for Visual Studio 2015, 2017, and 2019, but I won't have the time for it soon.

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