Define fmtlib_headers am: e6b0113482 am: 5dd4549077 am: 5748635696 am: e8244f58ae

Original change: https://android-review.googlesource.com/c/platform/external/fmtlib/+/1922597

Change-Id: I2fc708c66f56fa2087e7377fc11606727ed8c5ef