support multi-arch for operator-sdk build (#1605)

Author: vincent-pli

cmd/operator-sdk/build/cmd.go

@@ -88,7 +88,13 @@ func buildFunc(cmd *cobra.Command, args []string) error {
 	}
 
 	projutil.MustInProjectRoot()
-	goBuildEnv := append(os.Environ(), "GOOS=linux", "GOARCH=amd64")
+	goBuildEnv := append(os.Environ(), "GOOS=linux")
+
+	if value, ok := os.LookupEnv("GOARCH"); ok {
+		goBuildEnv = append(goBuildEnv, "GOARCH="+value)
+	} else {
+		goBuildEnv = append(goBuildEnv, "GOARCH=amd64")
+	}
 
 	// If CGO_ENABLED is not set, set it to '0'.
 	if _, ok := os.LookupEnv("CGO_ENABLED"); !ok {