Merge topic 'ci-warning-flags'

b51127249e ci: Enable -Wstrict-prototypes in tests for merge request pipelines
58d5f34d31 Replace deprecated -Werror-implicit-function-declaration with -Werror=
78c0935c9b Enable -Wundefined-func-template when building CMake's C++ code
2c6dde430a Enable -Wstrict-prototypes when building CMake's C code

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !10983