composefs fails to build with musl

[fboudra]

composefs fails to build when using latest musl:

tools/mountcomposefs.c warnings and 2: errors generated.
43:20: error: call to undeclared function 'basename'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   43 |         const char *bin = basename(argv0);
      |                           ^
tools/mountcomposefs.c:43:14: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Wint-conversion]
   43 |         const char *bin = basename(argv0);
      | 

Details on https://errors.yoctoproject.org/Errors/Details/761688/

For reference: https://git.musl-libc.org/cgit/musl/commit/?id=725e17ed6dff4d0cd22487bb64470881e86a92e7