gnu: qemu: Build with support for Linux AIO

Add libaio as an input, such that QEMU is built with support for Asynchronous
I/O (AIO).

* gnu/packages/virtualization.scm (qemu)[inputs]: Uncomment libaio.

gnu/packages/virtualization.scm

@@ -145,7 +145,7 @@ (define-public qemu
      `(("alsa-lib" ,alsa-lib)
        ("attr" ,attr)
        ("glib" ,glib)
-       ;; ("libaio" ,libaio)
+       ("libaio" ,libaio)
        ("libattr" ,attr)
        ("libcap" ,libcap)           ; virtfs support requires libcap & libattr
        ("libjpeg" ,libjpeg-8)