bump NDK toolchain to 4.9

[dulmandakh]

This PR will bump NDK_TOOLCHAIN_VERSION to 4.9 or use GCC 4.9 to build C++ code. Once merged, we can bump folly to a newer version, which requires GCC 4.9.

Test Plan:

Everything build and run as usual.

Release Notes:

[ANDROID] [ENHANCEMENT] [NDK] - bump NDK_TOOLCHAIN_VERSION to 4.9

[dulmandakh]

Please review @hramos@mdvacca

[hramos]

Also cc @fkgozali

[dulmandakh]

@fkgozali please review and merge

[dulmandakh]

Or maybe #19893, which does the same but also bumps NDK version. I tried every NDK version, and r14b was the latest version to compile with minimal code changes.

[facebook-github-bot]

@hramos has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[dulmandakh]

@hramos is there any issue regarding merging this PR? I was able to compile RN with latest NDK, and would like to create a PR once this merged.

[hramos]

@dulmandakh No, no issues. We try to avoid landing diffs late on Friday afternoons. I'll get this going today.

[react-native-bot]

This pull request was closed by @dulmandakh in ccdd450.

Once this commit is added to a release, you will see the corresponding version tag below the description at ccdd450. If the commit has a single master tag, it is not yet part of a release.