Allow += define without preceding = or := ?

[Jan Kratochvil]

Hi,

I am using some '.am' include file(s) for each directory for features like:

 * global: Provide '.h' files dependencies checking etc.
 * subdirectories: Compile different types of .c files with different options.
                   (library part vs. non-UNIX code vs. library clients etc.)

Therefore I need to 'append' ('+=') to some "primaries"/options from included
'.am' filse although I cannot predict such "primary"/option is already defined
('=' or ':=') by our parent Makefile.am.

Currently I use empty pre-defines of all "primaries"/options used across the
project in one 'Makefile-head.am' to solve it. Unfortunately it creates big and
slow 'Makefile.in's scattered across the directories.

* Solution #0: It is not an option to optimize empty "primaries" out of
  'Makefile.in's as they should remain overridable from make(1) command-line
  even if set unconditionally as empty. I expect it would be possible to safely
  omit them if even the corresponding 'EXTRA_$&' variable would be empty/unset.

* Solution #1: Introduce some 'AUTOMAKE_OPTIONS' item to permit '+=' without
  preceding '=' or ':='.

Or did I miss something? Thanks for advice. Willing to possibly code it.



Regards,
Jan Kratochvil

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