multimedia/aom: unbreak build on aarch64 after f0f115af84c3
CMake Error at build/cmake/aom_configure.cmake:212 (enable_language):
The CMAKE_ASM_COMPILER: as is not a full path and was not found in the PATH. Tell CMake where to find the compiler by setting either the environment variable "ASM" or the CMake cache entry CMAKE_ASM_COMPILER to the full
path
to the compiler, or to the compiler name if it is in the PATH.
Reported by: eduardo