Fix ifdef so that only tier-1 platforms are building the plugin sdk.

Fixing OS/2 tinderbox bustage.

modules/plugin/Makefile.in

@@ -56,12 +56,10 @@ endif
 endif
  
 ifdef ENABLE_TESTS
-ifeq (,$(filter WINNT Darwin Linux,$(OS_ARCH)))
-ifneq ($(OS_ARCH),BeOS)
+ifneq (,$(filter WINNT Darwin Linux,$(OS_ARCH)))
 DIRS		+= tools/sdk
 endif
 endif
-endif
 
 include $(topsrcdir)/config/rules.mk