Upload build metrics after a build is completed.

Soong now supports the ability to upload metrics to another location
by setting the ANDROID_ENABLE_METRICS_UPLOAD to an uploader that
accepts the upload.proto proto buffer message. When the environment
variable is set, a set of build metrics files (soong_metrics,
rbe_metrics.pb and build_error) is uploaded.

Bug: 140638454
Test: * Wrote unit test cases
      * Setup the uploader, built a succcessful and failed aosp_arm-eng
        target and monitor the uploading of the metrics.
Change-Id: I76a65739c557dc90345e098ca03119a950ece2d2
diff --git a/ui/build/config_test.go b/ui/build/config_test.go
index df618c4..7b14c47 100644
--- a/ui/build/config_test.go
+++ b/ui/build/config_test.go
@@ -26,6 +26,7 @@
 	"testing"
 
 	"android/soong/ui/logger"
+	"android/soong/ui/status"
 )
 
 func testContext() Context {
@@ -33,6 +34,7 @@
 		Context: context.Background(),
 		Logger:  logger.New(&bytes.Buffer{}),
 		Writer:  &bytes.Buffer{},
+		Status:  &status.Status{},
 	}}
 }