drivers/Makefile.am: reword default NUTSW_DRIVERLIST_DUMMY_UPS to avo…

…id automake rewrites and actually not-conflict building dummy-ups twice

Signed-off-by: Jim Klimov <[email protected]>

drivers/Makefile.am

@@ -51,10 +51,14 @@ if HAVE_LIBREGEX
   AM_CFLAGS += $(LIBREGEX_CFLAGS)
 endif
 
-# Allow top-level Makefile override NUTSW_DRIVERLIST_DUMMY_UPS="" to run
+# Allow top-level Makefile override NUTSW_DRIVERLIST_DUMMY_UPS="dummy" to run
 # a build scenario without this driver (it is in a different dependency)
-NUTSW_DRIVERLIST_DUMMY_UPS = dummy-ups
-NUTSW_DRIVERLIST = $(NUTSW_DRIVERLIST_DUMMY_UPS) clone clone-outlet apcupsd-ups skel
+# NOTE: Must be defaulted with EXEEXT to avoid rewrites by automake parser
+# which defeat the purpose of it being optionally built via `make all/drivers`
+# in top level.
+NUTSW_DRIVERLIST_DUMMY_UPS = dummy-ups$(EXEEXT)
+NUTSW_DRIVERLIST = $(NUTSW_DRIVERLIST_DUMMY_UPS) \
+ clone clone-outlet apcupsd-ups skel
 SERIAL_DRIVERLIST = al175 bcmxcp belkin belkinunv bestfcom	\
  bestfortress bestuferrups bestups etapro everups 	\
  gamatronic genericups isbmex liebert liebert-esp2 liebert-gxe masterguard metasys	\