aco: use c++17

std::map::try_emplace requires C++17, so we need to make sure we're
compiling with C++17 enabled.

Fixes: 8aff7152a0 ("aco: make IDSet sparse")
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23047>

src/amd/compiler/meson.build

@@ -96,6 +96,7 @@ _libaco = static_library(
   gnu_symbol_visibility : 'hidden',
   build_by_default : true,
   cpp_args : [cpp_args_aco, cpp_msvc_compat_args],
+  override_options: ['cpp_std=c++17'],
 )
 
 # Also link with aco