acos.s fix: use the formula acos(x) = atan2(sqrt(1-x),sqrt(1+x))
[musl] / crt /
drwxr-xr-x   ..
drwxr-xr-x - arm
-rw-r--r-- 0 crt1.c
-rw-r--r-- 0 crti.c
-rw-r--r-- 0 crtn.c
drwxr-xr-x - i386
drwxr-xr-x - x86_64