Improvements to libtool support.

Improvements to the libtool support in QEMU. Replace hard coded
libtool in the infrastructure with $(LIBTOOL) and allow
overriding the libtool binary used via the configure
script.

Reviewed-by: Andreas F=E4rber <andreas.faerber@web.de>
Signed-off-by: Brad Smith <brad@comstyle.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/rules.mak b/rules.mak
index 1a2622c..884d421 100644
--- a/rules.mak
+++ b/rules.mak
@@ -22,7 +22,7 @@
 	@echo "missing libtool. please install and rerun configure"; exit 1
 else
 %.lo: %.c
-	$(call quiet-command,libtool --mode=compile --quiet --tag=CC $(CC) $(QEMU_INCLUDES) $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) -c -o $@ $<,"  lt CC $@")
+	$(call quiet-command,$(LIBTOOL) --mode=compile --quiet --tag=CC $(CC) $(QEMU_INCLUDES) $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) -c -o $@ $<,"  lt CC $@")
 endif
 
 %.o: %.S