The configure check subsystem relies on generating diagnostics to detect unsupported flags. One some platforms, this requires that -Werror be in play in order for those diagnostics to be fatal. However, the --disable-warnings-as-errors flag inhibits application of -Werror. This can result in configure checks returning surprising results. In particular, if a user has passed an invalid flag in by setting CCFLAGS or similar on the command line but has also applied --disable-warnings-as-errors, the build may proceed despite the erroneous flag. We should ensure that the effect of --disable-warnings-as-errors applies only to our source code, and not to our configure checks.