dev-libs/glib: Exclude nonsensical and broken libelf dep on Windows

dev-libs/glib: Exclude nonsensical and broken libelf dep on Windows

elfutils (via libelf) does not build on Windows. gresources are not
embedded within ELF binaries on that platform anyway and inspecting
ELF binaries from other platforms is not that useful so exclude the
dependency in this case.

For what it's worth, dev-libs/libelf was tried as an alternative but
while Meson did pick it up and link it, gresource.exe still reported
that ELF support was missing.

Closes: https://github.com/gentoo/gentoo/pull/15337
Package-Manager: Portage-2.3.99, Repoman-2.3.22
Signed-off-by: James Le Cuirot <chewi@gentoo.org>