Ship the JSON firmware "descriptor files"
    
    From version 4.1 (due in August 2019) onwards, QEMU ships the so-called
    firmware "descriptor files".  These are small JSON files that describe
    details about UEFI firmware binaries — such as the fimware binary path,
    its architecture, supported machine type, NVRAM template and so forth.
    
    You can see examples of these files from the QEMU upstream Git:
    https://git.qemu.org/?p=qemu.git;a=tree;f=pc-bios/descriptors
    
        $> tree descriptors/
        descriptors/
        ├── 50-edk2-i386-secure.json
        ├── 50-edk2-x86_64-secure.json
        ├── 60-edk2-aarch64.json
        ├── 60-edk2-arm.json
        ├── 60-edk2-i386.json
        └── 60-edk2-x86_64.json
    
    QEMU 4.1 itself will ship the above files.  However, Fedora needs to
    ship these file as part of its EDK2 package.
    
    Why?
    ----
    
    (1) Quoting (with minor formatting edits) Laszlo Ersek:
    
          Distributions providing their own EDK2 packages would not include
          the descriptors from upstream QEMU, even if they otherwise package
          QEMU.  That's beause the descriptor files in QEMU match the
          firmware bundled with QEMU -- but the firmware images in the
          distros' own EDK2 packages are different.  So, if a distro
          provides an EDK2 package, then the same EDK2 package should offer
          matching descriptors.  QEMU offers descriptors (soon) because QEMU
          technically distributes edk2 firmware binaries (soon).  [Where
          "soon" == QEMU 4.1]
    
    (2) And as Dan Berrangé reminded on IRC:
    
          In Fedora, we need to ship them [the "descriptor files"] as part
          of the EDK2 package, because Fedora throws away all the firmware
          files that QEMU bundles, because we're [Fedora] required to
          rebuild everything from pristine source.
    
                        - - -
    
    In this patch:
    
    (*) Use the firmware descriptor files provided by Laszlo (thanks!) in
        this comment here:
        https://bugzilla.redhat.com/show_bug.cgi?id=1728652#c2 ("RFE: Ship
        the JSON firmware "descriptor files" as part of EDK2").
    
        On the double-digit priority prefixes, refer to the rationale here:
        https://src.fedoraproject.org/rpms/edk2/pull-request/3#comment-27523
    
    (*) Install the JSON files for the relevant architectures in
        `/usr/share/qemu/firmware`, as required by specification[+].  And
        make each EDK2 own this directory; multiple RPMs owning the same
        directory is no problem.
    
    [+] https://git.qemu.org/?p=qemu.git;a=blob;f=docs/interop/firmware.json
    
    Resolves: rhbz#1728652
    
    Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>