gstreamer-full: Properly export gst_init_static_plugins for Win32 PE

Currently, GStreamer relies throughout on ELF (and MachO)'s symbol
table preserving the function address, instead of marking it as
exportable, either through visibility:default or __declspec(dllexport).

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5194>

meson.build

@@ -437,6 +437,7 @@ if building_full
   # Build shared library
   gstfull = build_target('gstreamer-full-1.0',
     init_static_plugins_c,
+    c_args: ['-DBUILDING_GST'],
     target_type: get_option('gst-full-target-type'),
     link_args: gstfull_link_args,
     link_whole : exposed_libs,
@@ -445,7 +446,7 @@ if building_full
     install : true,
   )
   gst_full_c_flags =  []
-  if building_full_static
+  if building_full_static or get_option('default_library') == 'static'
     gst_full_c_flags += ['-DGST_STATIC_COMPILATION']
   endif
 

scripts/generate_init_static_plugins.py

@@ -14,6 +14,7 @@ $dynamic_types_declaration
 $plugins_declaration
 $giomodules_declaration
 
+_GST_EXPORT
 void
 gst_init_static_plugins (void)
 {