fix "Meson encountered an error in file meson.build, line 19, column … (#1536)

fix "Meson encountered an error in file meson.build, line 19, column 8: Unknown method "set_install_script" in object."

authors.txt

@@ -71,3 +71,4 @@ Michal Sojka
 Aaron Small
 Joe Baldino
 Peter Harris
+Roger Boerdijk

manual tests/4 standalone binaries/meson.build

@@ -16,12 +16,12 @@ if host_machine.system() == 'darwin'
   install_data('Info.plist',
   install_dir : 'Contents')
 
-  meson.set_install_script('osx_bundler.sh')
+  meson.add_install_script('osx_bundler.sh')
 endif
 
 if host_machine.system() == 'linux'
   install_data('myapp.sh', install_dir : '.')
-  meson.set_install_script('linux_bundler.sh')
+  meson.add_install_script('linux_bundler.sh')
 endif
 
 extra_link_args = []