Arch cmake Qt5Qml dependency

[Vedrillan]

When running cmake on master (0887ef745cf2e513a98f812e960787cc06827e55) it fails with the following message

-- Could NOT find Qt5Qml (missing: Qt5Qml_DIR)
CMake Warning at 3rdparty/qt5.cmake:3 (find_package):
  Found package configuration file:

    /usr/lib64/cmake/Qt5/Qt5Config.cmake

  but it set Qt5_FOUND to FALSE so package "Qt5" is considered to be NOT
  FOUND.  Reason given by package:

  Failed to find Qt5 component "Qml" config file at
  "/usr/lib64/cmake/Qt5Qml/Qt5QmlConfig.cmake"



Call Stack (most recent call first):
  rpcs3/CMakeLists.txt:34 (include)


-- Configuring done
CMake Error at rpcs3/CMakeLists.txt:54 (add_executable):
  Target "rpcs3" links to target "Qt5::Qml" but the target was not found.
  Perhaps a find_package() call is missing for an IMPORTED target, or an
  ALIAS target is missing?


CMake Error at rpcs3/CMakeLists.txt:54 (add_executable):
  Target "rpcs3" links to target "Qt5::Qml" but the target was not found.
  Perhaps a find_package() call is missing for an IMPORTED target, or an
  ALIAS target is missing?


CMake Error at rpcs3/rpcs3qt/CMakeLists.txt:10 (add_library):
  Target "rpcs3_ui" links to target "Qt5::Qml" but the target was not found.
  Perhaps a find_package() call is missing for an IMPORTED target, or an
  ALIAS target is missing?

This component is provided by the package qt5-declarative in Arch, after installing this additional package the build end in success.

This dependency qt5-declarative should probably be added to the README dependency list for Arch.

[AniLeo]

Addressed by #5525