package/lvm2: disable for musl toolchains

package/lvm2: disable for musl toolchains

lvm2 doesn't build with musl toolchains due to several assignment of read-only
variable like stdin, stdout and stderr.
Also, it use mallinfo function which is not available with musl.

These issues has been reported upstream [2] but some of them remains
even with the latest stable release 2.02.163.

Fixes:
http://autobuild.buildroot.net/results/3d4df873a3d4fa199e03d8aa8694eafeac474e5a
[...]

[1] http://lists.busybox.net/pipermail/buildroot/2016-August/170592.html
[2] https://www.redhat.com/archives/linux-lvm/2016-February/msg00024.html

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>