meson: add wrap for libdrm

This allows building Mesa with the Android NDK, which doesn't provide
libdrm.

We will generate an `Android.bp` file using the `ninja-to-soong` tool
(https://github.com/rjodinchr/ninja-to-soong), and to do this we run
Mesa's standard meson build system to generate the ninja commands that
we then translate to soong.

That meson invocation is done using the Android NDK, which doesn't
provide libdrm, so until we find an alternative solution[*] we provide a
wrap file that builds libdrm as part of the Mesa build (but does not
install it--we still use the Android-provided libdrm at runtime)

Co-authored-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35058>

meson.build

@@ -1670,12 +1670,18 @@ if _drm_blame != ''
   message('libdrm @0@ needed because @1@ has the highest requirement'.format(_drm_ver, _drm_blame))
 endif
 
+allow_fallback_for_libdrm = get_option('allow-fallback-for').contains('libdrm')
+
 # Then get each libdrm module
 foreach d : _libdrm_checks
   if d[1]
     set_variable(
       'dep_libdrm_' + d[0],
-      dependency('libdrm_' + d[0], version : '>=' + _drm_ver)
+      dependency(
+        'libdrm_' + d[0],
+        version : '>=' + _drm_ver,
+        allow_fallback: allow_fallback_for_libdrm,
+      )
     )
   endif
 endforeach
@@ -1684,7 +1690,8 @@ with_gallium_drisw_kms = false
 if system_has_kms_drm
   dep_libdrm = dependency(
     'libdrm', version : '>=' + _drm_ver,
-    required : with_dri2 or with_dri or with_gbm
+    required : with_dri2 or with_dri or with_gbm,
+    allow_fallback: allow_fallback_for_libdrm,
   )
 else
   # We should prevent libdrm from being available when the target doesn't have it to avoid transitive

meson.options

@@ -832,3 +832,13 @@ option(
   value : false,
   description : 'Install the drivers internal shader compilers (if needed for cross builds).'
 )
+
+option(
+  'allow-fallback-for',
+  type : 'array',
+  value : [],
+  choices : [
+    'libdrm',
+  ],
+  description : 'Allows the fallback mechanism if the dependency is not available on the system, or too old.'
+)

subprojects/libdrm.wrap

@@ -0,0 +1,6 @@
+[wrap-file]
+directory = libdrm-2.4.123
+source_url = https://dri.freedesktop.org/libdrm/libdrm-2.4.123.tar.xz
+source_filename = libdrm-2.4.123.tar.xz
+source_hash = a2b98567a149a74b0f50e91e825f9c0315d86e7be9b74394dae8b298caadb79e
+wrapdb_version = 2.4.123-1