platform: fix compatibility with ln(1) without relative support

(cherry picked from commit 0e5992a)

Author: q66

platform/meson.build

@@ -17,12 +17,15 @@ fs_mod = import('fs')
 ln_exe = find_program('ln', native: true)
 platform_plugin_symlinks = []
 foreach platform_plugin : platform_plugin_targets
+    inp_fp = platform_plugin.full_path()
+    inp_name = fs_mod.name(inp_fp)
+    rel_inp = fs_mod.name(fs_mod.parent(inp_fp)) / inp_name
     platform_plugin_symlinks += [
         custom_target(
-            'link-@0@'.format(fs_mod.name(platform_plugin.full_path()).underscorify()),
-            output: fs_mod.name(platform_plugin.full_path()),
+            'link-@0@'.format(inp_name.underscorify()),
+            output: inp_name,
             input: platform_plugin,
-            command: [ln_exe, '-srnf', '@INPUT@', '@OUTPUT@'],
+            command: [ln_exe, '-sf', rel_inp, '@OUTPUT@'],
             build_by_default: true,
         )
     ]