tools/zlib: move zlib build to tools

This allows us to link the other tools against our libz and we do not
need the system zlib any more.

Only the static linked library is copied to the staging directory so we
have a statically linked library on all systems and not only on Linux.
This also adds the new dependencies of the packages which are depending
on zlib.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Tested-by: Koen Vandeputte <koen.vandeputte@ncentric.com>

tools/make-ext4fs/patches/100-add-ldflags.patch

@@ -0,0 +1,11 @@
+--- a/Makefile
++++ b/Makefile
+@@ -27,7 +27,7 @@ OBJ := \
+ 	$(CC) $(CFLAGS) -c -o $@ $^
+ 
+ make_ext4fs: $(OBJ) libsparse/libsparse.a
+-	$(CC) -o $@ $^ $(ZLIB)
++	$(CC) $(LDFLAGS)-o $@ $^ $(ZLIB)
+ 
+ libsparse/libsparse.a:
+ 	$(MAKE) -C libsparse/ libsparse.a