Add ability to only upload a single Chromium build and check for patch existence

ct/go/master_scripts/build_chromium/main.go

Index: ct/go/master_scripts/build_chromium/main.go
diff --git a/ct/go/master_scripts/build_chromium/main.go b/ct/go/master_scripts/build_chromium/main.go
index 48e484f663c6bfb9e80703d5bc26fa77a925e33d..c10108008ede9496877876d69d30cae72853b620 100644
--- a/ct/go/master_scripts/build_chromium/main.go
+++ b/ct/go/master_scripts/build_chromium/main.go
@@ -90,7 +90,7 @@ func main() {
 		return
 	}
 
-	if _, _, err := util.CreateChromiumBuild("", *targetPlatform, *chromiumHash, *skiaHash, *applyPatches); err != nil {
+	if _, _, err := util.CreateChromiumBuild("", *targetPlatform, *chromiumHash, *skiaHash, *applyPatches, false); err != nil {

[dogben, 2016/05/18 14:29:37]

Seems like this always would want to upload just a single build with patches?

So, would it make sense for CreateChromiumBuild to not build the unpatched
version if both applyPatches and uploadSingleBuild are true?

[rmistry, 2016/05/19 11:21:00]

The (applyPatches && !uploadSingleBuild) was confusing so I now just check for
!uploadSingleBuild. This means that if applyPatches is false and
uploadSingleBuild is false then two patchless builds will be created and
uploaded, we do not have a usecase for this yet but does not hurt to have the
ability to do that.

[dogben, 2016/05/19 14:09:08]

Oh, I see. I was confused, but the new code is less confusing. :-)

 		glog.Errorf("Error while creating the Chromium build: %s", err)
 		return
 	}