meson: implement split-debug

split-debug uses C args `--gsplit-dwarf` and linker args `--gdb-index`
to achieve split debug, speed up the CI linking, and allow us to
distribute debug symbols standalone.

Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Signed-off-by: David Heidelberg <david.heidelberg@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28576>

meson.build

@@ -961,6 +961,22 @@ endif
 # otherwise define MESA_DEBUG to 0
 pre_args += '-DMESA_DEBUG=' + (with_mesa_debug ? '1' : '0')
 
+with_split_debug = get_option('split-debug') \
+  .disable_if(not cc.compiles('''#include<stdio.h>
+                                 int main() {
+                                 printf("\n");
+                                 };''',
+                    args : '-gsplit-dwarf',
+                    name : 'split-dwarf support'),
+    error_message : 'split-debug requires compiler -gsplit-dwarf support') \
+  .disable_if(not cc.has_link_argument('-Wl,--gdb-index'),
+    error_message : 'split-debug requires the linker argument -Wl,--gdb-index')
+
+if with_split_debug.allowed() and get_option('debug')
+  add_project_arguments('-gsplit-dwarf', langauge : ['c', 'cpp'])
+  add_project_link_arguments('-Wl,--gdb-index', language : ['c', 'cpp'])
+endif
+
 with_shader_cache = get_option('shader-cache') \
   .require(host_machine.system() != 'windows', error_message : 'Shader Cache does not currently work on Windows') \
   .allowed()

meson_options.txt

@@ -1,6 +1,12 @@
 # Copyright © 2017-2019 Intel Corporation
 # SPDX-License-Identifier: MIT
 
+option(
+  'split-debug',
+  type : 'feature',
+  value : 'disabled',
+  description : 'split debug information (-gsplit-dwarf compile flag) and debug information in the gdb index format (--gdb-index)',
+)
 option(
   'platforms',
   type : 'array',