vpython: clear DEPOT_TOOLS_DIR before running scripts

Once we're done using DEPOT_TOOLS_DIR to bootstrap ourselves, remove
it from the env so it isn't passed to the python script which might
in turn run commands from other depot_tools trees.  Like gclient and
running chromium/src/third_party/depot_tools/ programs.

Bug: 1470590
Change-Id: I3dee847e45896ee25f01054026805277fc373c37
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4764126
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Joanna Wang <jojwang@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>

vpython

@@ -42,11 +42,15 @@ export DEPOT_TOOLS_UNAME_S="${DEPOT_TOOLS_UNAME_S:-$(uname -s | tr '[:upper:]' '
 source "${DEPOT_TOOLS_DIR}/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
+# Don't pass this to the Python script as it might turn around and run commands
+# in other depot_tools dirs.
+base_dir="${DEPOT_TOOLS_DIR}"
+unset DEPOT_TOOLS_DIR
 case "${DEPOT_TOOLS_UNAME_S}" in
 mingw*|cygwin*)
   cmd.exe //c $0.bat "$@"
   ;;
 *)
-  exec "${DEPOT_TOOLS_DIR}/.cipd_bin/vpython" "$@"
+  exec "${base_dir}/.cipd_bin/vpython" "$@"
   ;;
 esac

vpython3

@@ -40,11 +40,15 @@ export DEPOT_TOOLS_UNAME_S="${DEPOT_TOOLS_UNAME_S:-$(uname -s | tr '[:upper:]' '
 source "${DEPOT_TOOLS_DIR}/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
+# Don't pass this to the Python script as it might turn around and run commands
+# in other depot_tools dirs.
+base_dir="${DEPOT_TOOLS_DIR}"
+unset DEPOT_TOOLS_DIR
 case "${DEPOT_TOOLS_UNAME_S}" in
 mingw*|cygwin*)
   cmd.exe //c $0.bat "$@"
   ;;
 *)
-  exec "${DEPOT_TOOLS_DIR}/.cipd_bin/vpython3" "$@"
+  exec "${base_dir}/.cipd_bin/vpython3" "$@"
   ;;
 esac