[2198] Build threads directory first because . depends on it

src/lib/util/Makefile.am

@@ -1,4 +1,5 @@
-SUBDIRS = . io unittests tests pyunittests python threads
+# InterprocessSyncFile has a dependency on isc::util::thread::Mutex
+SUBDIRS = threads . io unittests tests pyunittests python
 
 AM_CPPFLAGS = -I$(top_srcdir)/src/lib -I$(top_builddir)/src/lib
 AM_CPPFLAGS += -I$(top_srcdir)/src/lib/util -I$(top_builddir)/src/lib/util
@@ -31,7 +32,8 @@ libb10_util_la_SOURCES += random/random_number_generator.h
 
 EXTRA_DIST = python/pycppwrapper_util.h
 
-libb10_util_la_LIBADD = $(top_builddir)/src/lib/exceptions/libb10-exceptions.la
+libb10_util_la_LIBADD =  $(top_builddir)/src/lib/exceptions/libb10-exceptions.la
+libb10_util_la_LIBADD += $(top_builddir)/src/lib/util/threads/libb10-threads.la
 CLEANFILES = *.gcno *.gcda
 
 libb10_util_includedir = $(includedir)/$(PACKAGE_NAME)/util