Add dummy command to submakefiles

Add a dummy command to the all: rule in sub-makefiles.
This avoids "Nothing to be done for `all'." messages from make.
Signed-off-by: NPaul Brook <paul@codesourcery.com>

Makefile.hw

@@ -29,6 +29,8 @@ OBJS+= lsi53c895a.o esp.o
 OBJS+= dma-helpers.o sysbus.o
 
 all: $(HWLIB)
+# Dummy command so that make thinks it has done something
+	@true
 
 $(HWLIB): $(OBJS)
 

Makefile.target

@@ -128,6 +128,8 @@ kvm.o: CFLAGS+=$(KVM_CFLAGS)
 kvm-all.o: CFLAGS+=$(KVM_CFLAGS)
 
 all: $(PROGS)
+# Dummy command so that make thinks it has done something
+	@true
 
 #########################################################
 # cpu emulator library