build: Correctly quote square brackets in regular expression
build: Correctly quote square brackets in regular expression

Square brackets are quotation characters in autoconf, and need to be
further quoted to appear in the resulting script.

frida/vala,GNOME/vala,GNOME/vala,frida/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala