Make `is_flag_supported_inner` take an `&Tool` instead of a `&Path` #2149

Job	Run time
Test wasm32-wasip1-thread	33s
Test build-std (aarch64-tvos)	1m 48s
Test build-std (aarch64-tvos-sim)	1m 50s
Clippy	11s
MSRV (ubuntu-latest)	28s
Test build-std (x86_64-tvos)	1m 50s
MSRV (windows-latest)	44s
MSRV (macos-latest)	28s
Rustfmt	9s
semver-checks	8s
Test (stable)	1m 17s
Test CUDA support	33s
Test (beta)	1m 27s
Test wasm (wasm32-unknown-unknown)	23s
Test (nightly)	1m 23s
Test (linux32)	2m 0s
Test (macos)	4m 12s
Test (aarch64-macos)	1m 0s
Test (aarch64-ios)	1m 24s
Test (win32)	1m 29s
Test (win64)	2m 47s
Test (mingw32)	2m 5s
Test (mingw64)	2m 31s
Test (windows-2019)	2m 47s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	3m 37s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	4m 4s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	4m 13s
	45m 21s

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