Tests: add (broken) override_options test case

[MathieuDuponchelle]

This reproduces a case I encountered in a project, where a pkg-config
dependency (aws-cpp-sdk-s3) has -std=c++11 in its cflags, but the
project uses c++17 features and passes -std=c++17 through
override_options.

The final compile command has c++17 before c++11, causing compilation
to fail.

[jpakkane]

I would call this a bug in the pc file. It should not define the version to be used. The C++ standard libraries guarantee (as far as I can tell) that old and new code can be compiled and linked together and the result will work. If the code can not be used with an older version of C++ then its headers should have an #ifdef check for the version and error out if it is too old.

Still, that being said, we should probably detect this and either remove all -std flags coming from pc files or, at the very least, print an error.

[MathieuDuponchelle]

Still, that being said, we should probably detect this and either remove all -std flags coming from pc files or, at the very least, print an error.

Sounds fair to me