siso: Use bundled python to run siso

Similar to https://crrev.com/c/6395717, but for siso wrapper.
This allows the build steps to use the bundled Python.

Change-Id: I57d56622f204cb26e025f164f90c079089314180
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6395718
Auto-Submit: Junji Watanabe <jwata@google.com>
Commit-Queue: Junji Watanabe <jwata@google.com>
Reviewed-by: Fumitoshi Ukai <ukai@google.com>

siso

@@ -5,4 +5,4 @@
 # found in the LICENSE file.
 
 base_dir=$(dirname "$0")
-PYTHONDONTWRITEBYTECODE=1 exec python3 "$base_dir/siso.py" "$@"
+PYTHONDONTWRITEBYTECODE=1 exec "$base_dir/python-bin/python3" "$base_dir/siso.py" "$@"

siso.bat

@@ -8,5 +8,7 @@ setlocal
 :: standalone, but allow other PATH manipulations to take priority.
 set PATH=%PATH%;%~dp0
 
+set scriptdir=%~dp0
+
 :: Defer control.
-python3 "%~dp0\siso.py" "%*"
+@call %scriptdir%python-bin\python3 "%~dp0\siso.py" "%*"