meson: centralize rust handling

This bumps the req for everything, but I think that's fine, because one
part restricting to a lower rust version doesn't make much sense as we are
also not doing it generally for C or C++.

This also makes it easier for packagers to know what requires rust.

Reviewed-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30414>

meson.build

@@ -845,12 +845,15 @@ if with_gallium_rusticl
   if meson.version().version_compare('< 1.4.0')
     error('rusticl requires meson 1.4.0 or newer')
   endif
+endif
 
+if with_gallium_rusticl or with_nouveau_vk or with_tools.contains('etnaviv')
   add_languages('rust', required: true)
   rustc = meson.get_compiler('rust')
+  rust = import('rust')
 
   if rustc.version().version_compare('< 1.76')
-    error('rusticl requires Rust 1.76.0 or newer')
+    error('Mesa requires Rust 1.76.0 or newer')
   endif
 endif
 

src/etnaviv/isa/meson.build

@@ -95,9 +95,6 @@ if with_tools.contains('etnaviv')
     error('etnaviv requires meson 1.4.0 or newer')
   endif
 
-  add_languages('rust', required: true)
-  rust = import('rust')
-
   isa_bindings_rs = rust.bindgen(
     input : 'bindings.h',
     output : 'isa_bindings.rs',

src/gallium/frontends/rusticl/meson.build

@@ -2,7 +2,6 @@
 # SPDX-License-Identifier: MIT
 
 fs = import('fs')
-rust = import('rust')
 
 libmesa_rust_util_files = files(
   'util/lib.rs',

src/nouveau/compiler/meson.build

@@ -4,14 +4,6 @@ if meson.version().version_compare('< 1.3.0')
   error('NVK requires meson 1.3.0 or newer')
 endif
 
-add_languages('rust', required: true)
-rust = import('rust')
-
-rc = meson.get_compiler('rust')
-if rc.version().version_compare('< 1.73.0')
-  error('NAK requires Rust 1.73.0')
-endif
-
 bindgen_version = find_program('bindgen').version()
 
 if bindgen_version == 'unknown'

src/nouveau/headers/meson.build

@@ -70,9 +70,6 @@ executable(
 
 # Only generate Rust bindings for NVK
 if with_nouveau_vk
-  add_languages('rust', required: true)
-  rust = import('rust')
-
   cl_rs_generated = []
   foreach cl : nv_classes
     cl_rs_generated += custom_target(

src/nouveau/nil/meson.build

@@ -4,14 +4,6 @@ if meson.version().version_compare('< 1.3.0')
   error('NVK requires meson 1.3.0 or newer')
 endif
 
-add_languages('rust', required: true)
-rust = import('rust')
-
-rc = meson.get_compiler('rust')
-if rc.version().version_compare('< 1.73.0')
-  error('nil_rs requires Rust 1.73.0')
-endif
-
 prog_cbindgen = find_program(
   'cbindgen',
   required : true,