Makefile.am: omit $(top_builddir) from DEPS and LDADDS

BSD make is less liberal than GNU make in matching targets, and so it
tries to resolve the dependency `./libxml2.la` and fails to match the
target `libxml2.la`.

Author: flavorjones

Makefile.am

@@ -110,8 +110,8 @@ if WITH_XPTR_SOURCES
 libxml2_la_SOURCES += xlink.c xpointer.c
 endif
 
-DEPS = $(top_builddir)/libxml2.la
-LDADDS = $(top_builddir)/libxml2.la
+DEPS = libxml2.la
+LDADDS = libxml2.la
 
 
 m4datadir = $(datadir)/aclocal