[native_toolchain_c] Tools do not resolve from build hook on Windows.

[MichealReed]

The tool resolvers work in tests and outside of the build hook, but at least on Windows if I try to use them inside of the hook, it always fails.

I tried three, but there may be more. Tests emulating the build hook environment might be beneficial here.

[  +98 ms] [  +75 ms] Running `where vswhere.exe`.
[  +93 ms] [  +44 ms] INFO: Could not find files for the given pattern(s).

[        ]              Running `where ndk-build.cmd`.
[        ]            INFO: Could not find files for the given pattern(s).

[  +80 ms] [  +78 ms] Running `where clang.exe`.
[        ] [  +52 ms] Running `where vswhere.exe`.
[  +93 ms] [  +39 ms] INFO: Could not find files for the given pattern(s).

Maybe an environment variable issue from #32?

It's very difficult to diagnose which variable is missing in this sort of situation.

[dcharkes]

I think this should have been fixed by:

• [native_assets_builder] Fix env var typo #2112

I am a bit surprised we didn't notice that typo earlier. I suppose it is because we're passing in the toolchains from Flutter into the hooks in the CCompilerConfig. For Android targets that's the NDK toolchain. So, we never tried to find a default toolchain.

[MichealReed]

I think this should have been fixed by:

Seems so, thanks!