Correctly handle sketch.FullPath during export (#136)

Author: facchinm

Diff for: commands/compile/compile.go

@@ -181,7 +181,11 @@ func Compile(ctx context.Context, req *rpc.CompileReq, outStream io.Writer, errS
 	var exportPath *paths.Path
 	var exportFile string
 	if req.GetExportFile() == "" {
-		exportPath = sketch.FullPath
+		if sketch.FullPath.IsDir() {
+			exportPath = sketch.FullPath
+		} else {
+			exportPath = sketch.FullPath.Parent()
+		}
 		exportFile = sketch.Name + "." + fqbnSuffix
 	} else {
 		exportPath = paths.New(req.GetExportFile()).Parent()