pyoxidizer: force pip to not use pep517 in order to be able to install hg

Mercurial is not (yet) a pep517 package, but the presence of a pyproject.toml
file tells newer-ish versions of pip that it should be one.

This is related to 58fe6d127a01, and fixes pyoxidizer builds for the Heptapod
CI.

Differential Revision: https://phab.mercurial-scm.org/D11710

rust/hgcli/pyoxidizer.bzl

@@ -122,7 +122,7 b' def make_exe(dist):'
     )
 
     # Add Mercurial to resources.
-    exe.add_python_resources(exe.pip_install(["--verbose", ROOT]))
+    exe.add_python_resources(exe.pip_install(["--verbose", "--no-use-pep517", ROOT]))
 
     # On Windows, we install extra packages for convenience.
     if IS_WINDOWS: