4839, 3294 introduced build breakage on older Illumos build machines
The fix for issues 4839 and 3294 ("generated elfdump struct layouts by hand, shouldn't have", commit 894fa7ba) broke the build of gen_struct_layout in usr/src/cmd/sgs/elfdump on older Illumos machines:
../common/gen_struct_layout.c: In function 'gen_prfdinfo':
../common/gen_struct_layout.c:560: error: 'prfdinfo_t' undeclared (first use in this function)
This happens because prfdinfo_t is declared in sys/procfs.h, but the author of the fix forgot to add the appropriate CPPFLAGS for the build target environment into the Makefile rules, so the build was picking up the older sys/procfs.h from the host system instead (which lacked the structure definition). Newer Illumos machines that ship with a newer sys/procfs.h aren't affected, but older (oi_151a7) are.