netdumpd doesn't compile with MK_CASPER == no after c80cc4bb

[ngie-eign]

netdumpd relies explicitly on libcasper after c80cc4b, which doesn't work if the system doesn't have libcasper installed:

/usr/obj/home/ngie/git/netdumpd created for /home/ngie/git/netdumpd
$ make
echo netdumpd.full: /usr/lib/libc.a  >> .depend
cc  -O2 -pipe -I/home/ngie/git/netdumpd/. -O0   -g -MD  -MF.depend.netdumpd.o -MTnetdumpd.o -std=gnu99 -fstack-protector-strong -Wsystem-headers -Werror -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wunused-parameter -Wcast-align -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls -Wold-style-definition -Wno-pointer-sign -Wmissing-variable-declarations -Wthread-safety -Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable  -Qunused-arguments  -c /home/ngie/git/netdumpd/netdumpd.c -o netdumpd.o
/home/ngie/git/netdumpd/netdumpd.c:61:10: fatal error: 'libcasper.h' file not found
#include <libcasper.h>
         ^
1 error generated.
*** Error code 1

Stop.
make: stopped in /home/ngie/git/netdumpd

Commenting out that #include causes a number of build failures.

[markjdb]

This is expected - capsicum and libcasper are non-optional dependencies. We rely on capsicum to restrict client paths without having to parse and sanitize them in userland. Unfortunately, it's a bit of an all-or-nothing deal.

We could avoid using capsicum given interfaces like the proposals described here: https://lwn.net/Articles/723057/