Revert "enter_chroot: drop netrc support"

This reverts commit bebec09ca32f11c8f2d04e5ea0d0f44dfc9f6bf5.

Reason for revert: Change is causing an issue with Mistral.  We can
revert in the branch to recover that release while we sort out ToT.

Original change's description:
> enter_chroot: drop netrc support
> 
> We use gitcookies everywhere now, so stop trying to copy this file in.
> The logic for importing gitcookies has long existed here, so nothing
> else needs to be done.
> 
> BUG=chromium:1024979
> TEST=CQ passes
> 
> Change-Id: Iffe0da094c9bbf66ab172d607504e9ae997a5fea
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1918112
> Reviewed-by: Sean Abraham <seanabraham@chromium.org>
> Tested-by: Mike Frysinger <vapier@chromium.org>

Bug: chromium:1024979
Change-Id: Ic7b9c7b1ab0ab8e52248734ef79de59373685e27
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1960555
Reviewed-by: Mike Nichols <mikenichols@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/sdk_lib/enter_chroot.sh b/sdk_lib/enter_chroot.sh
index c32f7a9..9796402 100755
--- a/sdk_lib/enter_chroot.sh
+++ b/sdk_lib/enter_chroot.sh
@@ -82,6 +82,7 @@
   .gdata_cred.txt             # User/password for Google Docs on chromium.org
   .gdata_token                # Auth token for Google Docs on chromium.org
   .disable_build_stats_upload # Presence of file disables command stats upload
+  .netrc                      # May contain required source fetching credentials
   .inputrc                    # Preserve command line customizations
 )