The "[" link may be missing during OS boostrapping.
* build.sh: Convert "[ ... ]" to "test ..."
* maintMakefile: Ditto.
* scripts/copyright-update: Ditto
* tests/scripts/features/reinvoke: Ditto
* tests/scripts/features/targetvars: Ditto
* .ccls: Remove -std=c99: it disables __attribute__ causing warnings.
* .dir-locals.el: Force the C coding style to "gnu".
* make-gdb.py: Add GDB macros for pretty-printing GNU make structs.
* scripts/copyright-update: Use GNULIB_SRCDIR to find update-copyright.