SPECS: kf6-kfilemetadata: Align optional dependency handling

[Jingwiw]

Changes

• Make --without ffmpeg actually disable FFmpeg discovery in CMake.

  The spec already has %bcond ffmpeg 1. When the bcond is disabled, passing CMAKE_DISABLE_FIND_PACKAGE_FFmpeg=ON prevents CMake from picking FFmpeg up from the buildroot anyway.

  Source: CMakeLists.txt

  find_package(FFmpeg 57.48 COMPONENTS AVCODEC)
  if (AVCODEC_FOUND)
      find_package(FFmpeg 57.40 COMPONENTS AVFORMAT)
      if (AVFORMAT_FOUND)
          find_package(FFmpeg 55.27 COMPONENTS AVUTIL)
      endif()
  endif()
  set_package_properties(FFmpeg PROPERTIES DESCRIPTION "Video Tag reader"
                         URL "https://ffmpeg.org/" TYPE OPTIONAL
                         PURPOSE "Support for video metadata")

• Use pkgconfig(libattr) for xattr support.

  kfilemetadata requires xattr support on Linux and looks for the libattr header/library pair.

  Source: CMakeLists.txt

  if ( CMAKE_SYSTEM_NAME MATCHES "Linux" )
      find_package(Xattr)
      set_package_properties(Xattr PROPERTIES DESCRIPTION "library libattr "
          URL "https://savannah.nongnu.org/projects/attr"
          TYPE REQUIRED
          PURPOSE "Extended attribute shared library")
  endif()

  Source: FindXattr.cmake

  find_path(XATTR_INCLUDE sys/xattr.h
      /usr/include
      /usr/local/include
      ${CMAKE_INCLUDE_PATH}
      ${CMAKE_INSTALL_PREFIX}/usr/include
  )
  
  find_library(XATTR_LIB NAMES attr libattr
      PATHS
          ${CMAKE_LIBRARY_PATH}
          ${CMAKE_INSTALL_PREFIX}/lib
  )

• Use ebook-tools-devel for EPub support.

  The EPub finder checks for libepub and epub.h; those are development files, so the build dependency should be the devel package rather than the runtime tools package.

  Source: CMakeLists.txt

  find_package(EPub)
  set_package_properties(EPub PROPERTIES DESCRIPTION "Ebook epub reader"
                         URL "https://sourceforge.net/projects/ebook-tools/" TYPE OPTIONAL
                         PURPOSE "Support for epub metadata")

  Source: FindEPub.cmake

  find_library (EPUB_LIBRARIES
    NAMES epub libepub
  )
  
  find_path (EPUB_INCLUDE_DIR
    NAMES epub.h
  )
  
  include (FindPackageHandleStandardArgs)
  find_package_handle_standard_args (EPub DEFAULT_MSG EPUB_LIBRARIES EPUB_INCLUDE_DIR)

• Use pkgconfig(exiv2) for Exiv2.

  The local CMake finder consumes the Exiv2 pkg-config result as hints for header and library lookup, so the pkgconfig dependency is the direct provider interface.

  Source: FindLibExiv2.cmake from the kfilemetadata build dependency stack

  find_path(LibExiv2_INCLUDE_DIRS NAMES exiv2/exif.hpp
      HINTS ${PC_EXIV2_INCLUDEDIR}
  )
  
  find_library(LibExiv2_LIBRARIES NAMES exiv2 libexiv2
      HINTS ${PC_EXIV2_LIBRARY_DIRS}
  )

AIGC Declaration: CodeX with gpt5.5 was used as coding agent.

Signed-off-by: Jingwiw wangjingwei@iscas.ac.cn