BuildEnvironmentHelper Tests With Process Detection Logic Get Confused

[benvillalobos]

Issue Description

The new-and-improved process detection logic in BuildEnvironmentHelper confuses tests, which run a "fake" 64-bit MSBuild.exe in an x86 process.

The detection logic:

https://github.com/BenVillalobos/msbuild/blob/525eebc0f31f8c770ad7b1636866aa2a15850e41/src/Shared/BuildEnvironmentHelper.cs#L540-L546

Steps to Reproduce

Un-skip the relevant tests that were disabled in #7550 and run tests.

Expected Behavior

Actual Behavior

Analysis

Versions & Configurations

[benvillalobos]

There might be a property to control the architecture the tests run as.

These tests could probably be replaced with some uber-test that does something to the effect of "given some msbuild.exe in a reasonable directory, can you figure out:

1. The root
2. amd64 dir
3. etc
   properly?"