dir-locals: Treat G_* macros as including a semicolon

From https://source.puri.sm/Librem5/calls/-/merge_requests/332#note_159116

Otherwise without appending a semicolon explicitly to the macros, emacs will insist on indentation.

However, this does not really seem to work for me: It still indents.

From https://www.gnu.org/software/emacs/manual/html_node/ccmode/Macros-with-_003b.html:

This buffer-local variable specifies which macros have semicolons. After setting its value, you need to call c-make-macro-with-semi-re for it to take effect.

In my emacs session there is no c-make-macro-with-semi-re which I could call and even starting a new emacs session makes no difference.

/cc @guido.gunther @mohammed.sadiq