Use filegroup as genrule srcs.

Test: mmma hardware/interfaces -j64
Change-Id: If282ed5f4a87045d169fcea7ad648b046a5f1cfb
diff --git a/tests/expression/1.0/Android.bp b/tests/expression/1.0/Android.bp
index 1730aba..5279503 100644
--- a/tests/expression/1.0/Android.bp
+++ b/tests/expression/1.0/Android.bp
@@ -13,8 +13,7 @@
     tools: ["hidl-gen"],
     cmd: "$(location hidl-gen) -o $(genDir) -Lc++ -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport android.hardware.tests.expression@1.0",
     srcs: [
-        "IExpression.hal",
-        "IExpressionExt.hal",
+        ":android.hardware.tests.expression@1.0_hal",
     ],
     out: [
         "android/hardware/tests/expression/1.0/ExpressionAll.cpp",
@@ -27,8 +26,7 @@
     tools: ["hidl-gen"],
     cmd: "$(location hidl-gen) -o $(genDir) -Lc++ -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport android.hardware.tests.expression@1.0",
     srcs: [
-        "IExpression.hal",
-        "IExpressionExt.hal",
+        ":android.hardware.tests.expression@1.0_hal",
     ],
     out: [
         "android/hardware/tests/expression/1.0/IExpression.h",