add build-all to .PHONY rules

Signed-off-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Makefile

@@ -12,7 +12,7 @@ config-host.mak:
 endif
 
 .PHONY: all clean cscope distclean dvi html info install install-doc \
-	recurse-all speed tar tarbin test
+	recurse-all speed tar tarbin test build-all
 
 VPATH=$(SRC_PATH):$(SRC_PATH)/hw