Regenerate all BUILD files in vendor/ from scratch using gazelle

vendor/github.com/coreos/pkg/dlopen/BUILD

@@ -1,9 +1,4 @@
-package(default_visibility = ["//visibility:public"])
-
-load(
-    "@io_bazel_rules_go//go:def.bzl",
-    "go_library",
-)
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
 
 go_library(
     name = "go_default_library",
@@ -17,6 +12,7 @@ go_library(
     }),
     cgo = True,
     clinkopts = ["-ldl"],
+    visibility = ["//visibility:public"],
 )
 
 filegroup(
@@ -30,4 +26,5 @@ filegroup(
     name = "all-srcs",
     srcs = [":package-srcs"],
     tags = ["automanaged"],
+    visibility = ["//visibility:public"],
 )