meson: Check for bundled Vulkan/SPIR-V headers before adding them to …

…the include list.

This feature requires Meson 0.58 or newer.

meson.build

@@ -1,7 +1,8 @@
-project('dxvk', ['c', 'cpp'], version : 'v2.3', meson_version : '>= 0.49', default_options : [ 'cpp_std=c++17', 'warning_level=2' ])
+project('dxvk', ['c', 'cpp'], version : 'v2.3', meson_version : '>= 0.58', default_options : [ 'cpp_std=c++17', 'warning_level=2' ])
 
 cpu_family = target_machine.cpu_family()
 platform   = target_machine.system()
+fs = import('fs')
 
 cpp = meson.get_compiler('cpp')
 cc = meson.get_compiler('c')
@@ -33,11 +34,17 @@ if get_option('build_id')
   ]
 endif
 
-dxvk_include_dirs = [
-  './include',
-  './include/vulkan/include',
-  './include/spirv/include'
-]
+dxvk_include_dirs = ['./include']
+if fs.is_dir('./include/vulkan/include')
+  dxvk_include_dirs += ['./include/vulkan/include']
+elif not cpp.check_header('vulkan/vulkan.h')
+  error('Missing Vulkan-Headers')
+endif
+if fs.is_dir('./include/spirv/include')
+  dxvk_include_dirs += ['./include/spirv/include']
+elif not cpp.check_header('spirv/unified1/spirv.hpp')
+  error('Missing SPIRV-Headers')
+endif
 
 dep_displayinfo = dependency(
   'libdisplay-info',