[FAB-9133] Data race in TestGenerateDockerBuild2

Data race between setting the _generateDockerBuild function reference in
the test and using/reading it from within the go routine spawned by the
production code.

Resolved by shadowing the function reference on the stack before
launching the go routine.

Change-Id: Ic1f2de8bc9687d706ed4d65c69455ddbaa09fe21
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>

Author: sykesm

core/chaincode/platforms/platforms.go

@@ -170,10 +170,11 @@ func GenerateDockerBuild(cds *pb.ChaincodeDeploymentSpec) (io.Reader, error) {
 	// ----------------------------------------------------------------------------------------------------
 	input, output := io.Pipe()
 
+	generateDockerBuild := _generateDockerBuild
 	go func() {
 		gw := gzip.NewWriter(output)
 		tw := tar.NewWriter(gw)
-		err := _generateDockerBuild(platform, cds, inputFiles, tw)
+		err := generateDockerBuild(platform, cds, inputFiles, tw)
 		if err != nil {
 			logger.Error(err)
 		}