RFR: 8323672: Suppress unwanted autoconf added flags in CC and CXX [v7]

[Julian Waters]

On Thu, 18 Jan 2024 16:21:46 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>> [JDK-8323008](https://bugs.openjdk.org/browse/JDK-8323008) reports unwanted autoconf flags being added to the command line, and solves the issue by filtering out the added flags by force. This is not optimal however, as doing so leaves the autoconf message that the flags were added still displaying during the configure process, which is confusing. Instead, setting a couple of fields to disable the autoconf internals responsible for the unwanted flag is a cleaner solution
>
> Julian Waters has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Implement custom AC_PROG_CC and AC_PROG_CXX in util.m4

Haha, thanks both. Though one thing has been annoying me ever since I wrote this, it's the fact that no "AC_UNDEF" exists to erase macros defined by AC_DEFUN. Overwriting macros like this, especially macros that are part of the "autoconf standard library", is a little bit painful to me. On the other hand, not like there is another way either...
(I guess m4_undefine exists, but that seems to be more for macros defined with m4_define, though I have tried using it on macros defined by AC_DEFUN and it _did_ work)

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PR Comment: https://git.openjdk.org/jdk/pull/17401#issuecomment-1900508158