bp2build: don't generate a WORKSPACE.

bp2build doesn't need to generate a WORKSPACE file.

Also cleanup conversion_test.go.

Test: TH
Change-Id: Iba2f4b2f71d72ccf8b148cd11d78c190f93560c4
diff --git a/bp2build/conversion.go b/bp2build/conversion.go
index 787222d..6b47cd1 100644
--- a/bp2build/conversion.go
+++ b/bp2build/conversion.go
@@ -19,12 +19,13 @@
 	ruleShims map[string]RuleShim,
 	buildToTargets map[string]BazelTargets,
 	mode CodegenMode) []BazelFile {
-	files := make([]BazelFile, 0, len(ruleShims)+len(buildToTargets)+numAdditionalFiles)
 
-	// Write top level files: WORKSPACE. These files are empty.
-	files = append(files, newFile("", "WORKSPACE", ""))
+	var files []BazelFile
 
 	if mode == QueryView {
+		// Write top level WORKSPACE.
+		files = append(files, newFile("", "WORKSPACE", ""))
+
 		// Used to denote that the top level directory is a package.
 		files = append(files, newFile("", GeneratedBuildFileName, ""))