Missing basename in util/test-path.c on musl-based systems

In systems using musl as libc, eg. certain Gentoo profiles, tests of ell 
fail to build, with error:
clang -DHAVE_CONFIG_H -I.    -fvisibility=hidden -DUNITDIR=\""./unit/"\" 
-DCERTDIR=\""./unit/"\" -O2 -pipe -fsigned-char 
-Wno-unknown-warning-option -Wno-unknown-pragmas -c -o unit/test-path.o 
unit/test-path.c
unit/test-path.c:65:9: error: call to undeclared function 'basename'; 
ISO C99 and later do not support implicit function declarations 
[-Wimplicit-function-declaration]
    65 |         base = basename(tmp_path);
       |                ^
unit/test-path.c:65:9: note: did you mean 'l_basename'?
./ell/path.h:20:13: note: 'l_basename' declared here
    20 | const char *l_basename(const char *path);
       |             ^
unit/test-path.c:65:7: error: incompatible integer to pointer conversion 
assigning to 'char *' from 'int' [-Wint-conversion]
    65 |         base = basename(tmp_path);
       |              ^ ~~~~~~~~~~~~~~~~~~
2 errors generated.

Musl doesn't have GNU basename() in the string.h, only POSIX in libgen.h
See also: Gentoo bug https://bugs.gentoo.org/942788
second error appears to be a false positive.