code_style: move platform-dependent code to `SourceGit.Native.OS` #3783

Job	Run time
Build / Build macOS (Apple Silicon)	4m 22s
Prepare version string	5s
Build / Build macOS (Intel)	2m 54s
Build / Build Windows x64	3m 33s
Build / Build Linux (arm64)	3m 38s
Build / Build Linux	3m 11s
Build / Build Windows ARM64	3m 46s
Package / Package macOS (osx-x64)	18s
Package / Package macOS (osx-arm64)	26s
Package / Package Linux (linux-x64)	51s
Package / Package Linux (linux-arm64)	58s
Package / Package Windows (win-x64)	29s
Package / Package Windows (win-arm64)	30s
	25m 1s

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