Install cmake files into an arch-independent directory

The justification is similar as for the .pc file: the include directory
is arch-independent, so the cmake description should be too.

meson.build

@@ -28,12 +28,14 @@ import('pkgconfig').generate(
  dataonly: true,
 )
 
+shared_cmake_dir = get_option('prefix') / 'share/cmake/xbyak'
 if meson.version().version_compare('>=0.50.0')
  cmake = import('cmake')
 
  cmake.write_basic_package_version_file(
  name: meson.project_name(),
- version: meson.project_version()
+ version: meson.project_version(),
+ install_dir: shared_cmake_dir,
  )
 
  cmake_conf = configuration_data()
@@ -43,6 +45,7 @@ if meson.version().version_compare('>=0.50.0')
  cmake.configure_package_config_file(
  name: meson.project_name(),
  input: 'cmake'/'meson-config.cmake.in',
- configuration: cmake_conf
+ configuration: cmake_conf,
+ install_dir: shared_cmake_dir,
  )
 endif