Add independent flags to C or C++ files #1519

Job	Run time
MSRV (ubuntu-latest)	1m 7s
Test (stable)	1m 8s
MSRV (windows-latest)	1m 43s
Test CUDA support	32s
Test (beta)	1m 13s
Test build-std (aarch64-tvos)	1m 57s
Test (nightly)	1m 13s
Test build-std (aarch64-tvos-sim)	1m 48s
Rustfmt	13s
Test (linux32)	1m 39s
Test build-std (x86_64-tvos)	1m 54s
Clippy	23s
Test (macos)	2m 51s
Test (aarch64-macos)	1m 26s
semver-checks	16s
Test (aarch64-ios)	1m 27s
Test (win32)	2m 54s
Test (win64)	5m 7s
Test (mingw32)	2m 58s
Test (mingw64)	2m 40s
Test (windows-2019)	3m 21s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	3m 7s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	4m 21s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	5m 26s
	50m 44s

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