Read build context name before deleting build dir

Fixes mongoose-os#73

Author: plinss

Diff for: cli/build_remote.go

@@ -58,6 +58,8 @@ func buildRemote(bParams *build.BuildParams) error {
 
 	buildDir := moscommon.GetBuildDir(projectDir)
 
+	buildContextName, _ := ioutil.ReadFile(moscommon.GetBuildCtxFilePath(buildDir))
+
 	os.RemoveAll(buildDir)
 	if err := os.MkdirAll(buildDir, 0755); err != nil {
 		return errors.Annotatef(err, "failed to create build directory")
@@ -281,9 +283,9 @@ func buildRemote(bParams *build.BuildParams) error {
 		return errors.Trace(err)
 	}
 
-	if data, err := ioutil.ReadFile(moscommon.GetBuildCtxFilePath(buildDir)); err == nil {
+	if buildContextName != nil {
 		// Successfully read build context name, transmit it to the remote builder
-		if err := mpw.WriteField(moscommon.FormBuildCtxName, string(data)); err != nil {
+		if err := mpw.WriteField(moscommon.FormBuildCtxName, string(buildContextName)); err != nil {
 			return errors.Trace(err)
 		}
 	}