modules/input: Only build quartz module if we're targeting quartz

Otherwise the build is broken on GNU/Linux and Win32.

modules/input/Makefile.am

@@ -162,8 +162,10 @@ im_quartz_la_LIBADD = $(LDADDS)
 if INCLUDE_IM_QUARTZ
 STATIC_QUARTZ_MODULE = libstatic-im-quartz.la
 else
+if USE_QUARTZ
 QUARTZ_MODULE = im-quartz.la
 endif
+endif
 
 multipress_defs = -DMULTIPRESS_LOCALEDIR=\""$(mplocaledir)"\" -DMULTIPRESS_CONFDIR=\""$(sysconfdir)/gtk-2.0"\"
 im_multipress_la_CPPFLAGS = $(multipress_defs)