Update scripts for packaging wheels from bazel. * It turns out that bazel is not (easily) capable of producing artifacts named like setuptools expects. * Added a script to massage it to the right form.

diff --git a/packaging/python/README.md b/packaging/python/README.md
index 6fcae98..43499f1 100644
--- a/packaging/python/README.md
+++ b/packaging/python/README.md

@@ -55,6 +55,11 @@
 functional) version without TensorFlow kernels. This should not be done for
 released binaries but can help while developing.
 
+Note that bazel does not always build properly named artifacts. See the tool
+`hack_python_package_from_runfiles.py` to extract and fixup artifacts from
+a bazel-bin directory. If using this mechanism, then the environment variable
+`PYIREE_PYTHON_ROOT` should be set to a suitable temp directory.
+
 ```shell
 cd $IREE_SRC
 bazel build -c opt \

diff --git a/packaging/python/common_setup.py b/packaging/python/common_setup.py
index 149dbdf..7bd62c5 100644
--- a/packaging/python/common_setup.py
+++ b/packaging/python/common_setup.py

@@ -28,6 +28,10 @@
 
 
 def get_package_dir(prefix=("bindings", "python")):
+  explicit_root = os.environ.get("PYIREE_PYTHON_ROOT")
+  if explicit_root: return explicit_root
+
+  # Use env variables based on build system type.
   cmake_build_root = os.environ.get("PYIREE_CMAKE_BUILD_ROOT")
   bazel_build_root = os.environ.get("PYIREE_BAZEL_BUILD_ROOT")
 

diff --git a/packaging/python/hack_python_package_from_runfiles.py b/packaging/python/hack_python_package_from_runfiles.py
new file mode 100644
index 0000000..e82faae
--- /dev/null
+++ b/packaging/python/hack_python_package_from_runfiles.py

@@ -0,0 +1,101 @@
+#!/usr/bin/python
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Given a runfiles directory from a bazel build, does surgery to extract
+# a usable python package directory. In addition to the bazel directory
+# structure being unnecessarily obtuse, it is also really hard to actually
+# name files correctly. This affects python extension modules which must be
+# named with a specific extension suffix. Bazel is extremely unflexible and
+# we patch around it with this script. For the record, there are various ways
+# to write custom rules to do this more natively, but it is all complicated
+# and needless complexity. We opt for a script that is at least readable by
+# mere mortals and in one place.
+# Usage:
+#   ./this_script <dest_dir> <path to bazel-bin>
+
+import os
+import platform
+import shutil
+import sys
+import sysconfig
+
+
+FILE_NAME_MAP = {
+  "binding.so": "binding{}".format(sysconfig.get_config_var("EXT_SUFFIX")),
+  "binding.pyd": False,
+  "binding.dylib": False,
+}
+
+
+def get_exe_suffix():
+  if platform.system() == "Windows":
+    return ".exe"
+  else:
+    return ""
+
+
+def copy_prefix(dest_dir, runfiles_dir, prefix):
+  # And finally seek into the corresponding path in the runfiles dir.
+  # Aren't bazel paths fun???
+  # Note that the "iree_core" path segment corresponds to the workspace name.
+  pkg_dir = os.path.join(runfiles_dir, "iree_core", *prefix)
+  if not os.path.exists(pkg_dir): return
+  dest_dir = os.path.join(dest_dir)
+  for root, dirs, files in os.walk(pkg_dir):
+    assert root.startswith(pkg_dir)
+    dest_prefix = root[len(pkg_dir):]
+    if dest_prefix.startswith(os.path.sep): dest_prefix = dest_prefix[1:]
+    local_dest_dir = os.path.join(dest_dir, dest_prefix)
+    os.makedirs(local_dest_dir, exist_ok=True)
+    for file in files:
+      copy_file(os.path.join(root, file), local_dest_dir)
+
+
+def copy_file(src_file, dst_dir):
+  basename = os.path.basename(src_file)
+  dst_file = os.path.join(dst_dir, basename)
+  mapped_name = FILE_NAME_MAP.get(basename)
+  if mapped_name is False:
+    # Skip.
+    return
+  elif mapped_name is not None:
+    dst_file = os.path.join(dst_dir, mapped_name)
+  shutil.copyfile(src_file, dst_file, follow_symlinks=True)
+
+
+def main():
+  # Parse args.
+  dest_dir = sys.argv[1]
+  bazel_bin = sys.argv[2] if len(sys.argv) > 2 else os.path.join(
+      os.path.dirname(__file__), "..", "..", "bazel-bin")
+
+  # Find the path to the runfiles of the built target:
+  #   //bindings/python/packaging:all_pyiree_packages
+  runfiles_dir = os.path.join(
+      bazel_bin, "packaging", "python",
+      "all_pyiree_packages%s.runfiles" % (get_exe_suffix(),))
+  if not os.path.isdir(runfiles_dir):
+    print("ERROR: Could not find build target 'all_pyiree_packages':",
+          runfiles_dir)
+    print("Make sure to build target", "//packaging/python:all_pyiree_packages")
+    sys.exit(1)
+
+  copy_prefix(dest_dir, runfiles_dir, ("bindings", "python"))
+  copy_prefix(dest_dir, runfiles_dir,
+              ("integrations", "tensorflow", "bindings", "python"))
+
+
+if __name__ == "__main__":
+  main()