Compile system test binaries during make

Using check_PROGRAMS would postpone compiling the binaries needed by
system tests until `make check` would be called. Since it's preferable
to invoke pytest directly to run the system test suite, compile these
binaries without installing them during `make all` instead by using
noinst_PROGRAMS.

This removes the need to use TESTS= make -e check hack invoked from
pytest to work around this issue.

bin/tests/system/dlzexternal/driver/Makefile.am

@@ -4,7 +4,7 @@ AM_CPPFLAGS +=			\
 	$(LIBISC_CFLAGS)	\
 	$(LIBDNS_CFLAGS)
 
-check_LTLIBRARIES = dlzexternal.la
+noinst_LTLIBRARIES = dlzexternal.la
 
 dlzexternal_la_SOURCES =	\
 	driver.c		\