chore!: enable --windows_enable_symlinks by default (bazel-contrib#3663)

Supporting Windows without full symlink support is quite difficult
because we rely on symlinks in many places. Since Windows support is
mediocre already, just require symlinks to be enabled. Symlink support
in Windows has been around for a long time now and is available via
non-admin mechanisms such as DevMode.

Author: rickeylev

.bazelrc

@@ -5,6 +5,10 @@
 # To update the file, execute
 import %workspace%/.bazelrc.deleted_packages
 
+# Symlinks are used extensively because of runfiles, venvs, and other reasons.
+# Supporting otherwise is very complex with little benefit.
+startup --windows_enable_symlinks
+
 test --test_output=errors
 
 # Do NOT implicitly create empty __init__.py files in the runfiles tree.

CHANGELOG.md

@@ -58,6 +58,13 @@ END_UNRELEASED_TEMPLATE
 
 {#v0-0-0-changed}
 ### Changed
+
+**Breaking**
+* {obj}`--windows_enable_symlinks` is required. Add `startup
+  --windows_enable_symlinks` to your `.bazelrc` to enable Bazel using full
+  symlink support on Windows.
+
+Other changes:
 * (pypi) Update dependencies used for `compile_pip_requirements`, building
   sdists in the `whl_library` rule and fetching wheels using `pip`.