add support for detecting pcc's compiler runtime
in old versions of pcc, the directory containing libpcc.a was not in
the library path, and other options like -print-file-name may have
been needed to locate it. however, -print-file-name itself seems to
have been added around the same time that the directory was added to
the search path, and moreover, I see no evidence that older versions
of pcc are capable of building a working musl shared library. thus, it
seems reasonable to just test whether -lpcc is accepted.
Rich Felker