The musl-fts package implements the fts(3) functions fts_open, fts_read, fts_children, fts_set and fts_close, which are missing in musl libc.
Prepare musl-fts for compilation:
./bootstrap.sh ./configure --prefix=/usr
Compile the package:
make
This package does not come with a testsuite.
Install the package:
make install