meson: fails to compile with -Dpython=disabled flag.

We compile GObject-Introspection anyway (except for cross-builds, where
anyway we don't rely on local Python scripts), so even if not installing
the Python plug-ins, still use them locally.

meson.build

@@ -1852,7 +1852,7 @@ subdir('app-tools')
 gimp_run_env=environment()
 gimp_run_env.set('GIMP_GLOBAL_BUILD_ROOT', meson.global_build_root())
 
-if meson.can_run_host_binaries()
+if meson.can_run_host_binaries() and have_gobject_introspection
   if enable_console_bin
     gimp_real_exe = gimpconsole_exe
   else

plug-ins/python/meson.build

@@ -1,7 +1,3 @@
-if not have_python
-  subdir_done()
-endif
-
 plugins = [
   { 'name': 'colorxhtml' },
   { 'name': 'file-openraster' },
@@ -27,27 +23,31 @@ foreach plugin : plugins
   name = plugin.get('name')
   srcs = plugin.get('srcs', [name + '.py'])
 
-  install_data(srcs, install_dir: gimpplugindir / 'plug-ins' / name,
-               install_mode: 'rwxr-xr-x')
+  if have_python
+    install_data(srcs, install_dir: gimpplugindir / 'plug-ins' / name,
+                 install_mode: 'rwxr-xr-x')
+  endif
 
   foreach src : srcs
     # Ugly trick to copy Python plug-ins into subfolders so that we can run GIMP
     # from the build directory without installing it.
+    # To be run even if we don't install Python plug-ins so that we can
+    # still run them for in-build scripts.
     run_command(python, meson.project_source_root() / '.gitlab/cp-plug-in-subfolder.py',
                 meson.current_source_dir() / src, meson.current_build_dir() / name, check: true)
   endforeach
 endforeach
 
-# Fallback fix to the problem of non-configured interpreters
-if platform_windows and not meson.is_cross_build() and python.found()
-  python_config = configuration_data()
-  python_config.set('PYTHON_PATH', '')
+if have_python
+  # Fallback fix to the problem of non-configured interpreters
+  if platform_windows and not meson.is_cross_build() and python.found()
+    python_config = configuration_data()
+    python_config.set('PYTHON_PATH', '')
 
-  configure_file(
-    input : 'pygimp.interp.in',
-    output: 'pygimp.interp',
-    configuration: python_config,
-    install: true,
-    install_dir: gimpplugindir / 'interpreters',
-  )
+    configure_file(input : 'pygimp.interp.in',
+                   output: 'pygimp.interp',
+                   configuration: python_config,
+                   install: true,
+                   install_dir: gimpplugindir / 'interpreters')
+  endif
 endif