build: Check for GJS GIRs with new macros

This uses the new AX_PROG_GJS, AX_CHECK_GIRS_GJS, and
AX_CHECK_GIR_SYMBOLS_GJS macros in autoconf-archive to check for the
GJS path and the necessary GIR files in configure.ac

https://bugzilla.gnome.org/show_bug.cgi?id=766460