Issues with 'LANG='

[Werner LEMBERG]

It seems that the recent version of 'gettext' (0.21 from Dec. 2019) on
MacOS – at least on my Lion box – has changed language handling.  In
the NEWS file I read

  * Runtime behaviour:
    - The interpretation of the language preferences on macOS has been
      improved, especially in the case where a system locale does not
      exist for the combination of the selected primary language and
      the selected territory.

In my shell, `set | less` shows

  LANG=en_US.UTF-8
  LANGUAGE=de

Some test results:

   bison --help                    English output
   LANG= bison --help              German output
   LANGUAGE= bison --help          English output
   LANG=C bison --help             English output

I've reported in

  https://sourceforge.net/p/testlilyissues/issues/5753/

that `yyout2grammar.py` currently dies if it sees non-English Bison output.

Two possible fixes to our build system:

  * Use 'LANG=C' instead of 'LANG='.
  * Add 'LANGUAGE='.

What do you think?


    Werner