Aha! This ape/mp.h references the native lib not ape one. Applying the fix below and recompiling ape/lib/mp and ape/lib/sec eliminates the reference to /386/lib/libc.a, leaving just a few of unresolved references:
pcc -o 8.out bitmap.8 cache.8 channels.8 cliprdr.8 ewmhints.8 frpc.8 iso.8 licence.8 mcs.8 mppc.8 orders.8 pstcache.8 rdesktop.8 rdp.8 rdp5.8 seamless.8 secure.8 tcp.8 snarf.8 xkeymap.8 xwin.8
mpkaratsuba: undefined: mallocz
_PIPE: argv0: not defined
pcc: 8l: 8l 97689: error
The mp.h fix:
/n/sources/plan9/sys/include/ape/mp.h:5,12 - /sys/include/ape/mp.h:5,12
#ifndef __LIBMP_H_
#define __LIBMP_H_
- #pragma src "/sys/src/libmp"
- #pragma lib "libmp.a"
+ #pragma src "/sys/src/ape/lib/mp"
+ #pragma lib "/$M/lib/ape/libmp.a"
typedef unsigned int mpdigit; /* from /$objtype/include/u.h */