crunchgen: quiet -Wmissing-prototypes

[rlibby]

Test Plan

buildworld; installworld
/rescue/rescue (usage)
/rescue/rescue foo (usage)
/rescue/rescue ls

[markj]

Approved

[rlibby]

usr.sbin/crunch/crunchgen/crunchgen.c

1108 ↗

(On Diff #32333)

Whoops, that extra "\n" led to the following makefile template, from strings $(which crunchgen):

%s_stub.c:
        echo "extern int main(int argc, char **argv, char **envp);
int _crunched_%s_stub(int argc, char **argv, char **envp){return main(argc,argv,envp);}" >%s_stub.c
%s.lo: %s_stub.o $(%s_OBJPATHS)

I didn't notice earlier, apparently the build is using the installed crunchgen (rather than the one being built)?

New version replaces the line feed with a space and gives this from
strings /usr/obj/usr/src/freebsd/usr.sbin/crunch/crunchgen/crunchgen:

%s_stub.c:
        echo "extern int main(int argc, char **argv, char **envp); int _crunched_%s_stub(int argc, char **argv, char **envp){return main(argc,argv,envp);}" >%s_stub.c
%s.lo: %s_stub.o $(%s_OBJPATHS)

[rlibby]

Keep generated stub on one line.