Exporting MakeBazelTarget() in testing.go

Since we are putting conversion tests in the same
package as the module being converted from now on

Test: m bp2build
Change-Id: Ied53589d497fef70bfa11d8f6067459c9a50cd72
diff --git a/bp2build/aar_conversion_test.go b/bp2build/aar_conversion_test.go
index 8e7c2b5..ff82694 100644
--- a/bp2build/aar_conversion_test.go
+++ b/bp2build/aar_conversion_test.go
@@ -53,7 +53,7 @@
 }
 `,
 		ExpectedBazelTargets: []string{
-			makeBazelTarget(
+			MakeBazelTarget(
 				"android_library",
 				"TestLib",
 				AttrNameToString{
@@ -120,7 +120,7 @@
 }
 `,
 			ExpectedBazelTargets: []string{
-				makeBazelTarget(
+				MakeBazelTarget(
 					"aar_import",
 					"TestImport",
 					AttrNameToString{