The latest version does some funkyness.

[ianamason]

Both extract-bc and get-bc seem to be fooled by the build process.

Warning: Failed to find the file /vagrant/musllvm/obj/src/ldso/.dlopen.o.bc

because it isn't called o but rather lo:

 ls -la obj/src/ldso/.dlopen*
-rw-r--r-- 1 vagrant vagrant 1868 Apr 18 13:25 obj/src/ldso/.dlopen.lo.bc

Not sure why lo and o are different (in the reverse way):

ls -la obj/src/ldso/dlopen*
-rw-r--r-- 1 vagrant vagrant 1424 Apr 18 13:25 obj/src/ldso/dlopen.lo
-rw-r--r-- 1 vagrant vagrant 1392 Apr 18 13:23 obj/src/ldso/dlopen.o

[JL2210]

The reason is that *.lo files are Libtool object files, whereas *.o files are ELF/PE/Mach-O object files.
*.lo files are plain text documents that provide some info for the object file.