Low speed on x86_64-unknown-linux-musl

Why so different speed for some targets?
For x86_64-unknown-linux-gnu
```
./target/release/walk    
Time elapsed: 1.022172369s
Found 11 files
```
and x7 slow for x86_64-unknown-linux-musl
```
./target/x86_64-unknown-linux-musl/release/walk
Time elapsed: 7.560947213s
Found 11 files
```
Why?