Add all the sources to //:srcs filegroup and add a check to detect
missing file to it.

We need to activate this check on presubmits

--
Change-Id: Ia95e92d3816ce92bb69bc0e2cf56e9c60b68d970
Reviewed-on: https://bazel-review.googlesource.com/#/c/3949/
MOS_MIGRATED_REVID=126404792

scripts/release/BUILD

diff --git a/scripts/release/BUILD b/scripts/release/BUILD
index 7ccd9d5..a6a4ab0 100644
--- a/scripts/release/BUILD
+++ b/scripts/release/BUILD
@@ -1,6 +1,12 @@
 # Scripts for building Bazel releases
 package(default_visibility = ["//visibility:private"])
 
+filegroup(
+    name = "srcs",
+    srcs = glob(["**"]),
+    visibility = ["//scripts:__pkg__"],
+)
+
 sh_library(
     name = "relnotes",
     srcs = ["relnotes.sh"],