Rar2fs

git clone https://github.com/hasse69/rar2fs.git /tmp/rar2fs
wget -q http://www.rarlab.com/rar/unrarsrc-5.4.5.tar.gz -P /tmp/rar2fs/
tar -zxf /tmp/rar2fs/unrarsrc-5.4.5.tar.gz -C  /tmp/rar2fs
make -j$(($(nproc)+1)) -l$(($(nproc)+2)) -C  /tmp/rar2fs/unrar
make install-lib -C  /tmp/rar2fs/unrar
autoreconf -f -i /tmp/rar2fs/unrar
cd /tmp/rar2fs/; ./configure --with-unrar-lib=/tmp/rar2fs/unrar
make -j$(($(nproc)+1)) -l$(($(nproc)+2)) -C  /tmp/rar2fs
make install -C  /tmp/rar2fs
rm -rf /tmp/rar2fs

emerge --ask sys-fs/rar2fs