fix(sign): resolve signing issue caused by re-linking shared lib in *.eln files

When shared libs are stored in `Contents/Frameworks`, the re-link path
for `/usr/local/lib/gcc/11/libgcc_s.1.dylib` within bundled *.eln files
becomes `@executable_path/../Frameworks/libgcc_s.1.dylib`, which seems to
not leave enough space in the *.eln binary header to add a code
signature with codesign.

This used to work when shared libraries were bundled into
`Contents/MacOS/lib`, leading to a shorter relink path of
`@executable_path/lib/libgcc_s.1.dylib`, which does leave enough space
to add a code signature to *.eln files.

build-emacs-for-macos

@@ -747,7 +747,7 @@ class AbstractEmbedder
   end
 
   def lib_dir
-    File.join(app, 'Contents', 'Frameworks')
+    File.join(invocation_dir, 'lib')
   end
 end