meson: add radv to meson devenv

I either rebased this out of the original PR, just failed to commit it
and then reset it.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14879>

src/amd/vulkan/meson.build

@@ -213,3 +213,20 @@ radeon_icd = custom_target(
   install : true,
 )
 
+if meson.version().version_compare('>= 0.58')
+  _dev_icdname = 'radeon_devenv_icd.@0@.json'.format(host_machine.cpu())
+  custom_target(
+    'radeon_devenv_icd',
+    input : [vk_icd_gen, vk_api_xml],
+    output : _dev_icdname,
+    command : [
+      prog_python, '@INPUT0@',
+      '--api-version', '1.3', '--xml', '@INPUT1@',
+      '--lib-path', meson.current_build_dir() / icd_file_name,
+      '--out', '@OUTPUT@',
+    ],
+    build_by_default : true,
+  )
+
+  devenv.append('VK_ICD_FILENAMES', meson.current_build_dir() / _dev_icdname)
+endif