correct the linked libs on OpenBSD

Makefile

@@ -711,7 +711,7 @@ ifeq ($(PLATFORM),openbsd)
   SHLIBCFLAGS=-fPIC
   SHLIBLDFLAGS=-shared $(LDFLAGS)
 
-  THREAD_LIBS=-pthread
+  THREAD_LIBS=-lpthread
   LIBS=-lm
 
   CLIENT_LIBS =
@@ -721,7 +721,7 @@ ifeq ($(PLATFORM),openbsd)
 
   ifeq ($(USE_OPENAL),1)
     ifneq ($(USE_OPENAL_DLOPEN),1)
-      CLIENT_LIBS += $(THREAD_LIBS) -lossaudio -lopenal
+      CLIENT_LIBS += $(THREAD_LIBS) -lopenal
     endif
   endif