Harmonize build rule names to use hyphen instead of underscore

Change-Id: I31a4435d3f26edb6e9adbecdd88d8a9cedca8c0b

lib/junit/BUILD

diff --git a/lib/junit/BUILD b/lib/junit/BUILD
index c2a6fcc..3445f53 100644
--- a/lib/junit/BUILD
+++ b/lib/junit/BUILD
@@ -9,5 +9,5 @@
 
 java_library(
     name = "hamcrest-core",
-    exports = ["@hamcrest_core//jar"],
+    exports = ["@hamcrest-core//jar"],
 )