Pass cpp flags through in all cases to repository rule compilations (#1040)

Remove a line that prevents local builds of lxml to fail

python/pip_install/pip_repository.bzl

diff --git a/python/pip_install/pip_repository.bzl b/python/pip_install/pip_repository.bzl
index 511da34..d5d93f3 100644
--- a/python/pip_install/pip_repository.bzl
+++ b/python/pip_install/pip_repository.bzl
@@ -93,10 +93,6 @@
     if not rctx.os.name.lower().startswith("mac os"):
         return []
 
-    # Only update the location when using a hermetic toolchain.
-    if not is_standalone_interpreter(rctx, rctx.attr.python_interpreter_target):
-        return []
-
     # Locate xcode-select
     xcode_select = rctx.which("xcode-select")