Commit 7644d557df (Check*: Refactor variable handling, 2026-07-20,
v4.4.1~12^2~1) introduced a subtle regression in the handling of
`CMAKE_REQUIRED_LINK_OPTIONS` and `CMAKE_REQUIRED_LIBRARIES` which
resulted in an error if these were set to a 'false-like' value. This
could happen, for example, if the user passes `<name>_LIBS`, which
happens to have the value `<name>-NOTFOUND`. Previously, such values
would be ignored.
Fix it by separately checking for user- or module-provided link options
or link libraries. (We were already doing this for the other variables
used to propagate requirements into checks.)
Fixes: #28026
Commit a72e241200 (Check*: Restore more toleration of `;-W...` in
CMAKE_REQUIRED_FLAGS, 2026-07-21) updated the Check* modules to share
required-flag handling without adding coverage for those paths.
Exercise each probe with required definitions followed by a warning
option.
Without the compatibility handling, CMake rejects the warning option.
Without the required definitions, all seven checks fail to find their
header, functions, prototype, or type.
Issue: #28001
Matthew Woehlke
Josef Šimánek