lepton/cci: run stringer with "go run" (#96)

Run the stringer command (for code generation) using "go run" instead of
"go install" to avoid affecting the developer's global $GOBIN.

lepton/cci/cci.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
-//go:generate go install golang.org/x/tools/cmd/stringer@latest
+//go:generate -command stringer go run golang.org/x/tools/cmd/stringer@latest
 //go:generate stringer -output=strings_gen.go -type=CameraStatus,command,FFCShutterMode,FFCState,ShutterPos,ShutterTempLockoutState
 
 package cci