move bats_core BUILD to a file

deps.bzl

@@ -2,27 +2,13 @@
 # https://stackoverflow.com/questions/47192668/idiomatic-retrieval-of-the-bazel-execution-path#
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
-BATS_CORE_BUILD="""
-sh_library(
-  name = "bats_lib",
-  srcs = glob(["libexec/**"]),
-)
-
-sh_binary(
-  name = "bats",
-  srcs = ["bin/bats"],
-  deps = [":bats_lib"],
-  visibility = ["//visibility:public"],
-)
-"""
-
 def bazel_bats_dependencies(
     version="1.5.0",
     sha256="36a3fd4413899c0763158ae194329af8f48bb1ff0d1338090b80b3416d5793af",
 ):
     http_archive(
         name = "bats_core",
-        build_file_content = BATS_CORE_BUILD,
+        build_file = "@//:third_party/BUILD.bats_core",
         urls = [
             "https://github.com/bats-core/bats-core/archive/refs/tags/v%s.tar.gz" % version,
         ],

third_party/BUILD.bats_core

@@ -0,0 +1,11 @@
+sh_library(
+  name = "bats_lib",
+  srcs = glob(["libexec/**"]),
+)
+
+sh_binary(
+  name = "bats",
+  srcs = ["bin/bats"],
+  deps = [":bats_lib"],
+  visibility = ["//visibility:public"],
+)