Clone vulkan headers if needed

.gitmodules

@@ -1,6 +1,3 @@
 [submodule "modules/ImGui/src"]
 	path = modules/ImGui/src
 	url = https://github.com/flightlessmango/ImGui.git
-[submodule "modules/Vulkan-Headers"]
-	path = modules/Vulkan-Headers
-	url = https://github.com/KhronosGroup/Vulkan-Headers.git

meson.build

@@ -111,11 +111,6 @@ inc_common = [
 ]
 
 dep_vulkan = dependency('vulkan', required: get_option('use_system_vulkan'))
-if not dep_vulkan.found()
-  inc_common += [
-      include_directories('modules/Vulkan-Headers/include')
-  ]
-endif
 
 # Check for generic C arguments
 c_args = []
@@ -191,17 +186,17 @@ endif
 dep_pthread = cc.find_library('pthread')
 
 if dep_vulkan.found()
+  vulkan_headers = []
   datadir = get_option('datadir')
   if not datadir.startswith('/')
     datadir = get_option('prefix') / datadir
   endif
   vk_api_xml = files(datadir / 'vulkan/registry/vk.xml')
 else
-  vk_api_xml = files('modules/Vulkan-Headers/registry/vk.xml')
+  subdir('modules/Vulkan-Headers')
+  vulkan_headers = vk_api_xml
 endif
 
-vk_layer_table_helpers = []
-
 vk_enum_to_str = custom_target(
   'vk_enum_to_str',
   input : ['bin/gen_enum_to_str.py', vk_api_xml],

modules/Vulkan-Headers

@@ -1 +0,0 @@
-Subproject commit 7264358702061d3ed819d62d3d6fd66ab1da33c3

modules/Vulkan-Headers/clone_headers.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+GIT="$1"
+BUILD_DIR="$2"
+
+if [ ! -f "$BUILD_DIR/registry/vk.xml" ]; then
+  "$GIT" clone --depth 1 https://github.com/KhronosGroup/Vulkan-Headers.git "$BUILD_DIR"
+fi
+
+ln -sf "registry/vk.xml" modules/Vulkan-Headers/
+ln -sf "include/vulkan" modules/Vulkan-Headers/

modules/Vulkan-Headers/meson.build

@@ -0,0 +1,12 @@
+prog_git = find_program('git')
+prog_sh = find_program('sh')
+script_clone_hdrs = files('clone_headers.sh')
+
+vk_api_xml = custom_target(
+  'vk_api_xml',
+  input : [],
+  output : ['vk.xml'], # because output can't have segments, link vk.xml to this subdir dir in build prefix
+  command : [
+    prog_sh, script_clone_hdrs, prog_git, meson.current_build_dir()
+  ],
+)

src/meson.build

@@ -50,7 +50,7 @@ vklayer_mesa_overlay = shared_library(
   vk_enum_to_str,
   vklayer_files,
   overlay_spv,
-  vk_layer_table_helpers,
+  vulkan_headers,
   c_args : [
     pre_args,
     c_vis_args,