Use filegroup as hal genrule srcs.

Test: mma
Change-Id: I62d35fbd9dabee2ea1dfe146c5e7736e2ee6bec4
diff --git a/main.cpp b/main.cpp
index bd6c922..7426e65 100644
--- a/main.cpp
+++ b/main.cpp
@@ -608,6 +608,7 @@
         const FQName &packageFQName,
         const char *hidl_gen,
         Coordinator *coordinator,
+        const std::string &halFilegroupName,
         const std::string &genName,
         const char *language,
         const std::vector<FQName> &packageInterfaces,
@@ -628,9 +629,7 @@
 
     out << "srcs: [\n";
     out.indent();
-    for (const auto &fqName : packageInterfaces) {
-        out << "\"" << fqName.name() << ".hal\",\n";
-    }
+    out << "\":" << halFilegroupName << "\",\n";
     out.unindent();
     out << "],\n";
 
@@ -731,6 +730,7 @@
             packageFQName,
             hidl_gen,
             coordinator,
+            halFilegroupName,
             genSourceName,
             "c++",
             packageInterfaces,
@@ -749,6 +749,7 @@
             packageFQName,
             hidl_gen,
             coordinator,
+            halFilegroupName,
             genHeaderName,
             "c++",
             packageInterfaces,