Pass all environment variables to vendoring (#3964)

I have been struggling for a long time with getting private registries
and git repositories to work with vendoring. CARGO_REGISTR* is currently
broken due to a typo. Private git repositories don't work because the
ssh auth socket is not forwarded. And custom .ssh/config blow up if all
env variables referenced in the config are not forwarded.

There is no great way to forward all the right environment variables.
This does not appear to affect repinning directly in bzlmod.

Author: patrickmscott

crate_universe/private/crates_vendor.bzl

@@ -24,31 +24,19 @@ set -euo pipefail
 
 export RUNTIME_PWD="$(pwd)"
 if [[ -z "${{BAZEL_REAL:-}}" ]]; then
-    BAZEL_REAL="$(which bazel || echo 'bazel')"
+    export BAZEL_REAL="$(which bazel || echo 'bazel')"
 fi
 
 _BIN="$(rlocation "{bin}")"
 
-_ENVIRON=()
-_ENVIRON+=(BAZEL_REAL="${{BAZEL_REAL}}")
-_ENVIRON+=(BUILD_WORKSPACE_DIRECTORY="${{BUILD_WORKSPACE_DIRECTORY}}")
-_ENVIRON+=(PATH="${{PATH}}")
 {env}
 
-if [[ -n "${{CARGO_BAZEL_DEBUG:-}}" ]]; then
-    _ENVIRON+=(CARGO_BAZEL_DEBUG="${{CARGO_BAZEL_DEBUG}}")
-fi
-
-# Pass on CARGO_REGISTRIES_* and CARGO_REGISTRY*
-while IFS= read -r line; do _ENVIRON+=("${{line}}"); done < <(env | grep ^CARGO_REGISTER)
-
 # The path needs to be preserved to prevent bazel from starting with different
 # startup options (requiring a restart of bazel).
 # If you provide an empty path, bazel starts itself with
 # --default_system_javabase set to the empty string, but if you provide a path,
 # it may set it to a value (eg. "/usr/local/buildtools/java/jdk11").
-exec env - \\
-"${{_ENVIRON[@]}}" \\
+exec env -u OUTPUT_BASE \\
     "${{_BIN}}" \\
     {args} \\
     --nonhermetic-root-bazel-workspace-dir="${{BUILD_WORKSPACE_DIRECTORY}}" \\
@@ -143,13 +131,10 @@ def _sys_runfile_env(ctx, name, file, is_windows):
             name,
         )
 
-    return "\n".join([
-        "export {}=\"$(rlocation \"{}\")\"".format(
-            name,
-            _rlocationpath(file, ctx.workspace_name),
-        ),
-        "_ENVIRON+=({0}=\"${{{0}}}\")".format(name),
-    ])
+    return "export {}=\"$(rlocation \"{}\")\"".format(
+        name,
+        _rlocationpath(file, ctx.workspace_name),
+    )
 
 def _expand_env(value, is_windows):
     if is_windows: