Add open source build system support

Summary:
Add CMake and setup.py configuration for thrift-python OSS builds.

This is the first step toward `getdeps.py build fbthrift-python`. Manifests and workflows follow in subsequent diffs.

NOTE: To reduce cognitive load, the next change adds tests.

Reviewed By: vitaut

Differential Revision: D90828152

fbshipit-source-id: 31bd703f401fe151af5295176c15101f5a7407c0

Author: Satish Kumar

build/fbcode_builder/CMake/FindLibiberty.cmake

@@ -0,0 +1,29 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# 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
+#
+#     http://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.
+
+find_path(LIBIBERTY_INCLUDE_DIR NAMES libiberty.h PATH_SUFFIXES libiberty)
+mark_as_advanced(LIBIBERTY_INCLUDE_DIR)
+
+find_library(LIBIBERTY_LIBRARY NAMES iberty)
+mark_as_advanced(LIBIBERTY_LIBRARY)
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(
+  LIBIBERTY
+  REQUIRED_VARS LIBIBERTY_LIBRARY LIBIBERTY_INCLUDE_DIR)
+
+if(LIBIBERTY_FOUND)
+  set(LIBIBERTY_LIBRARIES ${LIBIBERTY_LIBRARY})
+  set(LIBIBERTY_INCLUDE_DIRS ${LIBIBERTY_INCLUDE_DIR})
+endif()