Changes are necessary to properly build libmesa_aco static library for Android.
was removed in 47de5532 "aco/isel: Move context initialization code to a dedicated file"
so filter-out of aco_instruction_selection_setup.cpp in Android is removed.

Fixes the following building errors:

FAILED: out/target/product/x86_64/obj/SHARED_LIBRARIES/vulkan.radv_intermediates/LINKED/vulkan.radv.so
...
ld.lld: error: undefined symbol: aco::setup_isel_context(aco::Program*, unsigned int, nir_shader* const*, ac_shader_config*, radv_shader_args*, bool)
>>> referenced by aco_instruction_selection.cpp:10879 (external/mesa/src/amd/compiler/aco_instruction_selection.cpp:10879)
>>>               aco_instruction_selection.o:(aco::select_program(aco::Program*, unsigned int, nir_shader* const*, ac_shader_config*, radv_shader_args*)) in archive out/target/product/x86_64/obj/STATIC_LIBRARIES/libmesa_aco_intermediates/libmesa_aco.a
...
ld.lld: error: undefined symbol: aco::init_context(aco::isel_context*, nir_shader*)
>>> referenced by aco_instruction_selection.cpp:10885 (external/mesa/src/amd/compiler/aco_instruction_selection.cpp:10885)
>>>               aco_instruction_selection.o:(aco::select_program(aco::Program*, unsigned int, nir_shader* const*, ac_shader_config*, radv_shader_args*)) in archive out/target/product/x86_64/obj/STATIC_LIBRARIES/libmesa_aco_intermediates/libmesa_aco.a

Fixes: 47de5532

 ("aco/isel: Move context initialization code to a dedicated file")
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6703>