Fix typo in configure, gracefully switch between M0 vs M1, skip
CC32/i686-unknown-linux-gnu-gcc targets if not available, esp. for
non-Guix usage.
* configure (M1): Declare missing variable.
* make.scm (main): all-go, clean-go: New targets.
* GNUmakefile (PHONY_TARGETS): Add them.
(.config.make): New target.
* guile/guix/make.scm (%CC32): Set to #f if not found.
(bin.gcc): Skip if CC not set.
(check-target?, add-target): Skip if target is not set.
822d0df889