const internal/goos.IsPlan9

3 uses

	internal/goos (current package)
		zgoos_linux.go#L22: const IsPlan9 = 0

	runtime
		malloc.go#L149: 	_NumStackOrders = 4 - goarch.PtrSize/4*goos.IsWindows - 1*goos.IsPlan9
		stack.go#L73: 	stackSystem = goos.IsWindows*4096 + goos.IsPlan9*512 + goos.IsIos*goarch.IsArm64*1024