Musl Installation
You must first make a src directory for sources.
mkdir -pv ~/lfz/src
cd ~/lfz/src
wget https://musl.libc.org/releases/musl-1.2.6.tar.gz
tar -xvf musl-1.2.6.tar.gz
cd musl-1.2.6
./configure --prefix=/usr --syslibdir=/lib
make -j$(nproc)
make DESTDIR=~/lfz/rootfs install
That should be it for musl installation if you followed the LF0 primary book as written.