1. Build x265
$wget https://bitbucket.org/multicoreware/x265_git/downloads/x265_3.2.1.tar.gz
$tar zxvf x265_3.2.1.tar.gz
$cd x265_3.2.1/build/linux
$./make-Makefiles.bash
$make && make install

2. Build ffmpeg

2.1 Prepare souce code
$git clone GitHub - ksvc/FFmpeg: mirror of git://source.ffmpeg.org/ffmpeg.git, with RTMP protocol extensions for H.265/HEVC powered by KSYUN.
$cd FFmpeg
$git reset --hard origin/release/3.4

2.2 Configure
./configure --enable-static --enable-pic \
        --disable-encoders --enable-encoder=aac --enable-encoder=libx264 --enable-gpl --enable-libx264 --enable-encoder=libx265  \

       --enable-libx265 --disable-decoders --enable-decoder=aac --enable-decoder=h264 --enable-decoder=hevc  --disable-demuxers \

       --enable-demuxer=aac --enable-demuxer=mov --enable-demuxer=mpegts --enable-demuxer=flv --enable-demuxer=h264 \

       --enable-demuxer=hevc --enable-demuxer=hls  --disable-muxers --enable-muxer=h264  --enable-muxer=flv --enable-muxer=f4v  \

       --enable-muxer=mp4 --disable-doc --extra-cflags="-fno-stack-check"

2.3 Build
$make -j4

2.4 Ttry
#push stream
$./ffmpeg -re -i 1.mp4 -c:a copy -c:v libx265 -f flv rtmp://192.168.1.1/live/hevc

#pull stream
$./ffplay rtmp://192.168.1.1/live/hevc

good luck!