treewide: enable pure Go by default

Pure can be safely enabled by default. For those targets which need cgo,
we can set `pure = "off"` on the go_binary or go_test.

This simplifies transitions, and makes the files/files_cc distinction
obsolete.

Change-Id: Ic1a985e7d347a7222f55735c1ee2016e8a7e1c65
Reviewed-on: https://review.monogon.dev/c/monogon/+/4158
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/osbase/build/fsspec/def.bzl b/osbase/build/fsspec/def.bzl
index 0165208..bcbf451 100644
--- a/osbase/build/fsspec/def.bzl
+++ b/osbase/build/fsspec/def.bzl
@@ -9,7 +9,7 @@
 def fsspec_core_impl(ctx, tool, output_file, extra_files = [], extra_fsspecs = []):
     """
     fsspec_core_impl implements the core of an fsspec-based rule. It takes
-    input from the `files`,`files_cc`, `symlinks` and `fsspecs` attributes
+    input from the `files`, `symlinks` and `fsspecs` attributes
     and calls `tool` with the `-out` parameter pointing to `output_file`
     and paths to all fsspecs as positional arguments.
     """
@@ -18,7 +18,7 @@
 
     fs_files = []
     inputs = []
-    for p, label in ctx.attr.files.items() + ctx.attr.files_cc.items() + extra_files:
+    for p, label in ctx.attr.files.items() + extra_files:
         if not p.startswith("/"):
             fail("file {} invalid: must begin with /".format(p))