GitLab

This patch improves the way we detect the host CPU architecture:

- It detects when we're running a 64-bit kernel with a 32-bit userland
  (and in this case, will default to using 32-bit binaries)

- It checks whether 64-bit binaries are available under
  $NDK/prebuilt/$HOST_TAG/bin/, and if not, it will default to
  32-bit binaries

- ndk-build: Ensure we use the prebuilt 'make' binary. This allows
  us to run the NDK on system where 'make' is not installed by default
  like Darwin without an XCode installation (another example is Windows
  but then ndk-build.cmd is used instead).

- ndk-build: Adds new log traces if NDK_LOG is defined to '1' or 'true'
  in either the environment or the command-line

- build/core/ndk-common.sh: this script is only used by the NDK development
  scripts under build/tools/. Update it to detect proper userland bitness.

Right now, we don't use/package 64-bit binaries yet, so this doesn't change
the NDK runtime, and only 32...