Much of the scripts in this directory have been shamelessly stolen from the Chromium parent in chromium/src/third_party/android_toolchain/. The Chromium Android NDK does not contain a full toolchain, as per CL 5106970.
While this decision makes sense for the Chromium team, there are dependencies (such as BoringSSL) which require a full NDK toolchain. Thus concludes the origin story of the infra/3pp/android_toolchain.