Merge "fmtlib: build and run the tests." am: 52b05fe0a0 am: 9dee828d17 am: 8fcbd9b817

Original change: https://android-review.googlesource.com/c/platform/external/fmtlib/+/1486343

Change-Id: I01959de46a06e4d2b8e33f88347bd104873bb1ce