Add GN target for jsr305.jar

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index eb1b2976a7cad3f5b7c5ef885796d4a1b6d433f3..ccd11339542c821c4139f3aadb2ee7dc5f0e6124 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -7,4 +7,8 @@ import("//build/config/android/rules.gni")
 # GYP: //third_party/findbugs:format_string_jar
 java_prebuilt("format_string_java") {
   jar_path = "lib/jFormatString.jar"
-}
+}
+
+java_prebuilt("jsr305_java") {
+  jar_path = "lib/jsr305.jar"
+}