Fix non-constant initializer error in libuuid.

Compiling libuuid was failing with the following error:

```c
libuuid/src/gen_uuid.c: In function 'uuid_generate_time_generic':
libuuid/src/gen_uuid.c:536:33: error: initializer element is not constant
  THREAD_LOCAL int  cache_size = cs_min;
```

The error was previously detected, and a fix was provided in
52abdf6a , where the GCC minimum version
was increased to 8 (GCC version 8 supports using const-declared
variables as constant expressions in some cases).

Unfortunately, the solution did not work as the `min_version` field of
the `[gcc]` section was being overwritten by its value in
`component/defaults.cfg`.
This is because `util-linux` (where libuuid config is located) is a
transient dependence of `defaults.cfg` through `python3`.

Fortunately, the error is already [patched upstream](https://github.com/util-linux/util-linux/commit/07e5c29d501c19e7af84fecb5915e0f9f94cb49f)
in version 2.40.1, so we can just upgrade the library to the latest
version instead, which we do here.

See merge request nexedi/slapos!1609

component/util-linux/buildout.cfg

@@ -6,14 +6,11 @@ extends =
   ../pkgconfig/buildout.cfg
   ../xz-utils/buildout.cfg
 
-[gcc]
-min_version = 8
-
 [util-linux]
 recipe = slapos.recipe.cmmi
 shared = true
-url = https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.39/util-linux-2.39.2.tar.xz
-md5sum = 2feb3e7c306f336a3d22a182dfffc942
+url = https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.40/util-linux-2.40.2.tar.xz
+md5sum = 88faefc8fefced097e58142077a3d14e
 configure-options =
   --disable-static
   --enable-libuuid