Hi,

while packaging the new version 1.21.2 of libheif (which now detects and compiles against libaom through CMake instead of pkgconf), I noticed missing dependencies on libaom-dev.

First problem (missing "aom-tools"):
-----
CMake Error at /usr/lib/x86_64-linux-gnu/cmake/AOM/AOMTargets.cmake:108 (message):
   The imported target "AOM::aomdec" references the file

      "/usr/bin/aomdec"

   but this file does not exist.  Possible reasons include:

   * The file was deleted, renamed, or moved to another location.

   * An install or uninstall procedure did not complete successfully.

   * The installation package was faulty and contained

      "/usr/lib/x86_64-linux-gnu/cmake/AOM/AOMTargets.cmake"

   but not all the files it references.

Call Stack (most recent call first):
   /usr/lib/x86_64-linux-gnu/cmake/AOM/AOMConfig.cmake:43 (include)
   cmake/modules/FindAOM.cmake:1 (find_package)
   CMakeLists.txt:224 (find_package)
-----

Adding "aom-tools" to the build-dependencies of libheif, the cmake step runs ("-- Found AOM: /usr/lib/x86_64-linux-gnu/cmake/AOM"), but now compilation fails due to missing libraries:
-----
/usr/bin/c++ -fPIC -g -O2 -ffile-prefix-map=/build/libheif-1.21.2=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -Wdate-time -D_FORTIFY_SOURCE=2              -shared -Wl,-z,relro -Wl,-z,now -Wl,--dependency-file=CMakeFiles/heif-aomenc.dir/link.d  -o libheif-aomenc.so "CMakeFiles/heif-aomenc.dir/encoder_aom.cc.o" "CMakeFiles/heif-aomenc.dir/__/error.cc.o" "CMakeFiles/heif-aomenc.dir/__/common_utils.cc.o" "CMakeFiles/heif-aomenc.dir/__/api/libheif/heif_plugin.cc.o"  -Wl,-rpath,/build/libheif-1.21.2/obj-x86_64-linux-gnu/libheif: /usr/lib/x86_64-linux-gnu/libaom.so.3.13.1 ../libheif.so.1.21.2 -lm -lyuv -lwebm
/usr/bin/ld: cannot find -lyuv: No such file or directory
/usr/bin/ld: cannot find -lwebm: No such file or directory
-----

Adding "aom-tools", "libwebm-dev" and "libyuv-dev" to the build dependencies of libheif fixes these issues.

I suggest adding the three packages to the Depends of "libaom-dev", so users of "libaom-dev" get the necessary dependencies automatically without having to depend on them themselves.

Thanks and best regards,
   Joachim