makefiles: Avoid nested variable expansion that doesn't work on BSD make.

dlls/Makedll.rules.in

@@ -10,7 +10,6 @@
 
 DLLFLAGS    = @DLLFLAGS@
 DLLEXT      = @DLLEXT@
-IMPLIBEXT   = @IMPLIBEXT@
 MINGWAR     = @MINGWAR@
 DEFS        = -D__WINESRC__ $(EXTRADEFS)
 BASEMODULE  = $(MODULE:%.dll=%)
@@ -20,7 +19,7 @@ WIN16_FILES = $(SPEC_SRCS16:.spec=.spec.o) $(C_SRCS16:.c=.o) $(EXTRA_OBJS16)
 ALL_OBJS    = @WIN16_FILES@ $(OBJS) $(RC_SRCS:.rc=.res)
 ALL_LIBS    = $(LIBPORT) $(EXTRALIBS) $(LDFLAGS) $(LIBS)
 IMPLIB_OBJS = $(IMPLIB_SRCS:.c=.o)
-IMPORTLIBFILE = $(IMPORTLIB:%=lib%.$(IMPLIBEXT))
+IMPORTLIBFILE = $(IMPORTLIB:%=lib%.@IMPLIBEXT@)
 STATICIMPLIB  = $(IMPORTLIBFILE:.def=.def.a)
 DLL_LDPATH  = -L$(DLLDIR) $(DELAYIMPORTS:%=-L$(DLLDIR)/%) $(IMPORTS:%=-L$(DLLDIR)/%)
 INSTALLDIRS = $(DESTDIR)$(dlldir) $(DESTDIR)$(datadir)/wine