skcms build updates

  - Never try to use LSAN on Mac, even locally.
  - Don't warn about f32 -> f16 conversions in f16 builds.
  - Roll NDK to r21d.

This is enough for `ninja` to run cleanly on my corp MBP,
using NDK 21 for Android builds.  So roll NDK to 21d.

Change-Id: I948727dd95c9fc888ccf6fb5ac34d16dc5249958
Reviewed-by: Brian Osman <>
Commit-Queue: Mike Klein <>
4 files changed