meson: work around meson 0.62 issue

Ubuntu 22.04 LTS has Meson 0.62, but recent versions of mesa fails to
build there due to an issue with using wayland-protocols from wrapdb,
that wasn't fixed until Meson 0.63. Luckily the problem is easy to
work around, so let's just do that.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/10232
Fixes: 5fe5c3e223 ("meson: add wayland-protocols from meson wrapdb")
Tested-by: Eero Tamminen <eero.t.tamminen@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26446>
(cherry picked from commit d8d49ad034)

.pick_status.json

@@ -174,7 +174,7 @@
         "description": "meson: work around meson 0.62 issue",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "5fe5c3e2231b58da7c3ce92d4f3cf0fd0d5f216b",
         "notes": null

src/egl/wayland/wayland-drm/meson.build

@@ -67,13 +67,13 @@ wp_files = {}
 foreach name, xml : wp_protos
   code = custom_target(
     name + '-protocol.c',
-    input : join_paths(wp_dir, xml),
+    input : files(join_paths(wp_dir, xml)),
     output : name + '-protocol.c',
     command : [prog_wl_scanner, wl_scanner_arg, '@INPUT@', '@OUTPUT@'],
   )
   header = custom_target(
     name + '-client-protocol.h',
-    input : join_paths(wp_dir, xml),
+    input : files(join_paths(wp_dir, xml)),
     output : name + '-client-protocol.h',
     command : [prog_wl_scanner, 'client-header', '@INPUT@', '@OUTPUT@'],
   )