GNU Bison options --header and --defines are not recognised by SCons when they don't have an argument

[piotrsiupa]

SCons ignores options --header and --defines passed to Bison when the argument is not provided.
The argument is optional for those options and if it is not provided SCons should behave the same way as if it encountered the options -d (which is detected correctly).
(https://www.gnu.org/software/bison/manual/bison.html#Output-Files)

• Link to SCons Users thread discussing your issue. - https://discord.com/channels/571796279483564041/571796280146133047/1087434623476301836
• Version of SCons - v4.5.1.49578b34582d9e92dac7d713a8e58599ae35aa63
• Version of Python - 3.10.6
• Which python distribution if applicable (python.org, cygwin, anaconda, macports, brew,etc) - the one from Ubuntu repository
• How you installed SCons - through pip
• What Platform are you on? (Linux/Windows and which version) - Linux Mint
• How to reproduce your issue? Please include a small self contained reproducer. Likely a SConstruct should do for most issues. - it's below
• How you invoke scons (The command line you're using "scons --flags some_arguments") - scons

targets = CFile('foo.y', YACCFLAGS='-d')
print('Flag `-d` (correct target list):', targets)

targets = CFile('bar.y', YACCFLAGS='--defines')
print('Flag `--defines` (incorrect target list):', targets)

targets = CFile('baz.y', YACCFLAGS='--header')
print('Flag `--header` (incorrect target list):', targets)

[mwichmann]

The code currently only recognizes the option if it includes an equals sign:

    fileGenOptions = ["--defines=", "--header=", "--graph="]

So we'd have to rework this a bit. Still doesn't look complicated.

[mwichmann]

Note to self (or whoever takes on implementing): the -g option defaults to a .gv file suffix. This suffix does not have a construction variable analogous to $YACCHFILESUFFIX - not sure if we need to add one, or can just hard-code it.