Makefile: update go.toolchain.rev atomically

Updates #501

Signed-off-by: James Tucker <[email protected]>

Author: raggi

Makefile

@@ -221,7 +221,8 @@ update-version: ## Update the version in build.gradle
 .PHONY: update-oss
 update-oss: ## Update the tailscale.com go module and update the version in build.gradle
 	GOPROXY=direct ./tool/go get tailscale.com@main
-	./tool/go run tailscale.com/cmd/printdep --go > go.toolchain.rev
+	./tool/go run tailscale.com/cmd/printdep --go > go.toolchain.rev.new
+	mv go.toolchain.rev.new go.toolchain.rev
 	./tool/go mod tidy -compat=1.23
 
 # Get the commandline tools package, this provides (among other things) the sdkmanager binary.