Add support for building .so

Makefile

@@ -1,10 +1,17 @@
 SRC=$(wildcard *.c)
 OBJ=$(patsubst %.c,%.o,$(SRC))
+LOBJ=$(patsubst %.c,%.lo,$(SRC))
 
 all: libpthread.a
 
 libpthread.a: $(OBJ)
 	$(AR) -rcs $@ $(OBJ)
 
+libpthread.so: $(LOBJ)
+	$(CC) $(CFLAGS) -nostdlib -shared -o $@ $(LOBJ)
+
 %.o: %.c
 	$(CC) $(CFLAGS) -I . -c $< -o $@
+
+%.lo: %.c
+	$(CC) $(CFLAGS) -fPIC -I . -c $< -o $@