Add build rules for building a library from src/utils files

This is an initial step on providing an alternative build system that
uses libraries from src subdirectories.

tests/Makefile

@@ -17,24 +17,24 @@ endif
 CFLAGS += -I../src
 CFLAGS += -I../src/utils
 
-OS_OBJS=../src/utils/os_unix.o
+LIBS = ../src/utils/libutils.a
 
+../src/utils/libutils.a:
+	$(MAKE) -C ../src/utils
 
 BASE64_OBJS=test-base64.o \
-	../src/utils/base64.o \
-	$(OS_OBJS)
+	$(LIBS)
 
 test-base64: $(BASE64_OBJS)
 	$(LDO) $(LDFLAGS) -o $@ $(BASE64_OBJS)
 
 
 MILENAGE_OBJS=test-milenage.o \
-	../src/utils/wpa_debug.o \
 	../src/crypto/aes-internal.o \
 	../src/crypto/aes-internal-enc.o \
 	../src/crypto/aes-encblock.o \
 	../src/crypto/milenage.o \
-	$(OS_OBJS)
+	$(LIBS)
 
 test-milenage: $(MILENAGE_OBJS)
 	$(LDO) $(LDFLAGS) -o $@ $(MILENAGE_OBJS)