Fix build without libtool

When libtool is not installed, automake calls the linker with the
library flags (`-llib`) _before_ the object files. In order to
successfully resolve symbols, the library flags need to come _after_ any
object file needing them. libtool does that correctly by itself, but
when automake cannot rely on libtool, we need to tell it about libraries
via `mybin_LDADD` instead of the global `AM_LDFLAGS`.

src/Makefile.am

@@ -3,13 +3,16 @@
 bin_PROGRAMS = dropwatch dwdump
 
 AM_CFLAGS = -g -Wall -Werror $(LIBNL3_CFLAGS) $(LIBNLG3_CFLAGS) $(READLINE_CFLAGS)
-AM_LDFLAGS = $(LIBNL3_LIBS) $(LIBNLG3_LIBS) $(READLINE_LIBS) -lpcap
+AM_LDFLAGS =
+ALL_LIBS = $(LIBNL3_LIBS) $(LIBNLG3_LIBS) $(READLINE_LIBS) $(LIBPCAP_LIBS)
+dropwatch_LDADD = $(ALL_LIBS)
+dwdump_LDADD = $(ALL_LIBS)
 AM_CPPFLAGS = -D_GNU_SOURCE
 
 dropwatch_SOURCES = main.c lookup.c lookup_kas.c
 dwdump_SOURCES = dwdump.c
 
 if USE_BFD
 dropwatch_SOURCES += lookup_bfd.c
-AM_LDFLAGS += -lbfd
+dropwatch_LDADD += -lbfd
 endif