x265 v3.2.1 does not build 10-bit (yuv420p10le, yuv422p10le or yuv444p10le)

[janngobble]

I installed ffmpeg @4.1.3_0+gpl2+nonfree. This installed (among other things) x264 & x265.

x264 installed and included all 10-bit support:

bash-3.2$ ffmpeg -h encoder=libx264 | grep pixel
    Supported pixel formats: yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p nv12 nv16 nv21 yuv420p10le yuv422p10le yuv444p10le nv20le gray gray10le

x265 installed and did not include ANY 10-bit support:

bash-3.2$ ffmpeg -h encoder=libx264 | grep pixel
   Supported pixel formats: yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p gbrp gray

bash-3.2$ x265 -V
x265 [info]: HEVC encoder version 3.2.1+1-b5c86a64bbbe
x265 [info]: build info [Mac OS X][clang 10.0.1][64 bit] 8bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2

How do we fix this? Thanks!