libubb/Makefile: build also a shared version of libubb; better cleanup

The improved cleanup removes the library after a partially successful build.

libubb/Makefile

@@ -1,8 +1,8 @@
 #
 # libubb/Makefile - Build the UBB library
 #
-# Written 2012 by Werner Almesberger
-# Copyright 2012 Werner Almesberger
+# Written 2012-2013 by Werner Almesberger
+# Copyright 2012-2013 Werner Almesberger
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,22 +13,32 @@
 
 TARGET = mipsel-openwrt-linux-
 CC = $(TARGET)gcc
+LD = $(TARGET)ld
 
-CFLAGS = -g -Wall -Iinclude
+CFLAGS = -g -Wall -fPIC -Iinclude
 LIB = libubb.a
+SHLIB = libubb.so
+LIBVERSION = 0.0.0
 
 OBJS = ubb.o swuart.o
 HDRS = ubb/ubb.h ubb/regbase.h ubb/regs4740.h ubb/swuart.h
 
 .PHONY:		all clean spotless
 
-all:		$(LIB)
+all:		$(SHLIB).$(LIBVERSION)
+
+$(SHLIB).$(LIBVERSION):	$(SHLIB)
+		/sbin/ldconfig -n .
+
+$(SHLIB):	$(LIB)
+		$(LD) -shared -soname $@.$(LIBVERSION) -o $@ \
+		    --whole-archive $^ || { rm -f $@; exit 1; }
 
 $(LIB):		$(OBJS)
-		$(AR) cr $@ $^
+		$(AR) cr $@ $^ || { rm -f $@; exit 1; }
 
 clean:
 		rm -f $(OBJS)
 
 spotless:	clean
-		rm -f $(LIB)
+		rm -f $(LIB) $(SHLIB) $(SHLIB).$(LIBVERSION)