Assignment to automatic variables

[cspiel]

OMake parses only one of the automatic
variables, when used in assigment namely @.
However, all others (&, *, +, <, >,
and ^) are un-assignable.

public.@ = target               # OK!

public.& = free-vals            # syntax error: parse error
public.* = stem                 # Failure: .public*: bad match
public.+ = all-deps-unsorted    # command not found in PATH: .public+
public.< = first-dep            # syntax error: parse error
public.> = no-suffix-target     # syntax error: parse error
public.^ = all-deps-sorted      # command not found in PATH: .public^

We can workaround the absence of assigning to public.*,
though as "$(public.*) == $(removesuffix $(public.@))"
holds.

Assigment is necessary as soon a any of
these variables must be expanded outside of a
rule body, e.g. for logging, printing, or just
viewing. Now print OPTIMIZATION_FLAGS, when
part of its definition reads

OPTIMIZATION_FLAGS += -fopt-info-optall=$`(removesuffix $(public.@)).opt-info