Simplified unit testing of sandboxing code.

sandbox/linux/seccomp-bpf/Makefile

 CFLAGS = -g -O3 -Wall -Werror -Wextra -Wno-missing-field-initializers -fPIC -I.
 CPPFLAGS = -D_GNU_SOURCE -DSECCOMP_BPF_STANDALONE -iquote ../../..
 LDFLAGS = -g -lpthread
 DEPFLAGS = -MMD -MF .$@.d
-MODS := demo sandbox_bpf util verifier
+MODS := demo sandbox_bpf die util verifier
 OBJS64 := $(shell echo ${MODS} | xargs -n 1 | sed -e 's/$$/.o64/')
 OBJS32 := $(shell echo ${MODS} | xargs -n 1 | sed -e 's/$$/.o32/')
 ALL_OBJS = $(OBJS32) $(OBJS64)
 DEP_FILES = $(wildcard $(foreach f,$(ALL_OBJS),.$(f).d))
 
 .SUFFIXES: .o64 .o32
 
 all: demo32 demo64
 
 clean:
         $(RM) demo32 demo64
         $(RM) *.o *.o32 *.o64 .*.d
         $(RM) core core.* vgcore vgcore.* strace.log*
 
 -include $(DEP_FILES)
 
 demo32: ${OBJS32}
         ${CXX} -m32 -o $@ $+ ${LDFLAGS}
 demo64: ${OBJS64}
         ${CXX} -m64 -o $@ $+ ${LDFLAGS}
 
 .cc.o32:
         ${CXX} -m32 ${CFLAGS} ${CPPFLAGS} ${DEPFLAGS} -c -o $@ $<
 .cc.o64:
         ${CXX} -m64 ${CFLAGS} ${CPPFLAGS} ${DEPFLAGS} -c -o $@ $<