Don't install tools if $(TOOLS) is empty, by Thayne Harbaugh.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3415 c046a42c-6fe2-441c-8c8c-71466251a162

Makefile

@@ -67,7 +67,9 @@ endif
 
 install: all $(if $(BUILD_DOCS),install-doc)
 	mkdir -p "$(DESTDIR)$(bindir)"
+ifneq ($(TOOLS),)
 	$(INSTALL) -m 755 -s $(TOOLS) "$(DESTDIR)$(bindir)"
+endif
 	mkdir -p "$(DESTDIR)$(datadir)"
 	for x in bios.bin vgabios.bin vgabios-cirrus.bin ppc_rom.bin \
 		video.x openbios-sparc32 pxe-ne2k_pci.bin \