stubdom: only build libxen*.a from tools/libs/

Avoid generating *.map files or running headers.chk when all we need
is the libxen*.a.

Also, allow force make to check again if libxen*.a needs rebuilt by
adding a '.PHONY' prerequisite.

Also, remove DESTDIR= as we don't do installation in this target, so
the value of DESTDIR doesn't matter.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

stubdom/Makefile

@@ -354,8 +354,8 @@ define BUILD_lib
  .PHONY: libxen$(1) clean-libxen$(1)
  libxen$(1): libs-$$(XEN_TARGET_ARCH)/$(1)/libxen$(1).a
  libs-$$(XEN_TARGET_ARCH)/$(1)/libxen$(1).a: $$(LIBDEPS_$(1)) $$(LIBDEP_$(1))
- libs-$$(XEN_TARGET_ARCH)/$(1)/libxen$(1).a: mk-headers-$$(XEN_TARGET_ARCH) $$(NEWLIB_STAMPFILE)
-	CPPFLAGS="$$(TARGET_CPPFLAGS)" CFLAGS="$$(TARGET_CFLAGS)" $$(MAKE) DESTDIR= CONFIG_LIBXC_MINIOS=y -C libs-$$(XEN_TARGET_ARCH)/$(1)
+ libs-$$(XEN_TARGET_ARCH)/$(1)/libxen$(1).a: mk-headers-$$(XEN_TARGET_ARCH) $$(NEWLIB_STAMPFILE) .phony
+	CPPFLAGS="$$(TARGET_CPPFLAGS)" CFLAGS="$$(TARGET_CFLAGS)" $$(MAKE) CONFIG_LIBXC_MINIOS=y -C $$(@D) $$(@F)
 
  clean-libxen$(1):
 	[ ! -e libs-$$(XEN_TARGET_ARCH)/$(1)/Makefile ] || $$(MAKE) DESTDIR= -C libs-$$(XEN_TARGET_ARCH)/$(1) clean