build: Use AM_PROG_CC_C_O
build: Use AM_PROG_CC_C_O

Use the Automake macro to enable per-target compiler flags.

ebassi/json-glib,brauliobo/json-glib,oerdnj/json-glib,brauliobo/json-glib,robtaylor/json-glib-gvariant,oerdnj/json-glib,GNOME/json-glib,brauliobo/json-glib,frida/json-glib,Distrotech/json-glib,robtaylor/json-glib-gvariant,GNOME/json-glib,ebassi/json-glib,oerdnj/json-glib,frida/json-glib,Distrotech/json-glib,Distrotech/json-glib,ebassi/json-glib,oerdnj/json-glib