Add Global CMake Build and OSS Tests (#1217)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1217

This updates the CMake build present for being able to share options, fixing up flags, etc. A GTest build is added as well, along with a script and VSCode debug target so that OSS contributors can very easily run and debug tests on any OS.

Note that this isn't completely done (need to revise Windows, Mac, documentation), but should be finished enough otherwise for review.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D42406686

fbshipit-source-id: 95e7ba5e4751c496a171785490e85cf0097fa839

cmake/yoga-config.cmake.in

@@ -0,0 +1,10 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/yogaTargets.cmake")
+
+check_required_components(yoga)