Cygwin: revamp localtime.o build rule

Rename localtime.c.patched to localtime.patched.c to keep the correct
language suffix.

Create localtime.patched.c in the build dir rather than in the source
dir.  Decouple the build rule for creating localtime.patched.c from
the rule to build localtime.o, so we don't have to rebuild the patched
source file all the time.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/Makefile.in

@@ -670,7 +670,7 @@ uninstall-man:
 	done
 
 clean distclean realclean:
-	-rm -f *.o *.dll *.dbg *.a *.exp junk *.base version.cc *.exe *.d *stamp* *_magic.h sigfe.s cygwin.def globals.h
+	-rm -f *.o *.dll *.dbg *.a *.exp junk *.base version.cc *.exe *.d *stamp* *_magic.h sigfe.s cygwin.def globals.h localtime.patched.c
 	-@$(MAKE) -C ${cygserver_blddir} libclean
 
 maintainer-clean: clean
@@ -734,9 +734,12 @@ dcrt0.o sigproc.o: child_info_magic.h
 
 shared.o: shared_info_magic.h
 
-localtime.o: $(srcdir)/tzcode/localtime_wrapper.c $(srcdir)/tzcode/localtime.c.patch
-	(cd $(srcdir)/tzcode && \
-		patch -u -o localtime.c.patched localtime.c localtime.c.patch)
+localtime.patched.c: tzcode/localtime.c tzcode/localtime.c.patch
+	patch -u -o localtime.patched.c \
+		    $(srcdir)/tzcode/localtime.c \
+		    $(srcdir)/tzcode/localtime.c.patch
+
+localtime.o: tzcode/localtime_wrapper.c localtime.patched.c
 	$(CC) ${COMMON_CFLAGS} ${localtime_CFLAGS} \
 		-I$(target_builddir)/winsup/cygwin \
 		-I$(srcdir) -I$(srcdir)/tzcode -c -o $@ $<

winsup/cygwin/tzcode/localtime_wrapper.c

@@ -122,7 +122,7 @@ tzgetwintzi (char *wildabbr, char *outbuf)
    (2) add conditional call to Cygwin's tzgetwintzi() from tzsetlcl()
    (3) add Cygwin's historical "posixrules" support to tzloadbody()
 */
-#include "localtime.c.patched"
+#include "localtime.patched.c"
 
 // Don't forget these Cygwin-specific additions from this point to EOF
 EXPORT_ALIAS (tzset_unlocked, _tzset_unlocked)