CMakeLists.txt: respect BUILD_TESTING

[ffontaine]

Don't build tests if the standard cmake BUILD_TESTING variable is set to OFF.

Signed-off-by: Fabrice Fontaine fontaine.fabrice@gmail.com

[joto]

Similar to #103 and just as unnecessary.

[ffontaine]

Thanks for pointing #103, I missed it.
However, in the context of embedded systems, this is not unnecessary as protozero fails to build on buildroot since its addition 2 days ago due to these tests. We have already 3 different build failures on the autobuilders.

Build fails on toolchains without wchar, extract from http://autobuild.buildroot.org/results/1cd/1cd24b757d87b963c70bc7ff927c6d983d0b142a/build-end.log:

[  7%] Building CXX object test/CMakeFiles/reader_tests.dir/reader_tests.cpp.o
In file included from /home/buildroot/autobuild/run/instance-0/output-1/build/protozero-1.7.0/test/include/test.hpp:4,
                 from /home/buildroot/autobuild/run/instance-0/output-1/build/protozero-1.7.0/test/unit/test_data_view.cpp:4:
/home/buildroot/autobuild/run/instance-0/output-1/build/protozero-1.7.0/test/catch/catch.hpp:1691:29: error: 'wstring' is not a member of 'std'
 1691 |     struct StringMaker<std::wstring> {
      |                             ^~~~~~~

Build fails on toolchains for sh4 (ICE), extract from http://autobuild.buildroot.org/results/3d8/3d8e841655a67ddaaa49ab9a93d1959b27d55cc7/build-end.log:

during RTL pass: final
In file included from /tmp/instance-1/output-1/build/protozero-1.7.0/test/t/repeated_packed_sint32/reader_test_cases.cpp:8:
/tmp/instance-1/output-1/build/protozero-1.7.0/test/include/packed_access.hpp: In function 'void ____C_A_T_C_H____T_E_S_T____24()':
/tmp/instance-1/output-1/build/protozero-1.7.0/test/include/packed_access.hpp:304:1: internal compiler error: in output_branch, at config/sh/sh.c:2755
  304 | }
      | ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://bugs.buildroot.net/> for instructions.

Build also fails if gcc is affected by bug 64735 (i.e. gcc < 7 on some architectures), extract from http://autobuild.buildroot.org/results/374/37468bec35713010ae3a10c0926ee0f5b482d874/build-end.log):

In file included from /nvme/rc-buildroot-test/scripts/instance-0/output-1/build/protozero-1.7.0/test/include/test.hpp:4:0,
                 from /nvme/rc-buildroot-test/scripts/instance-0/output-1/build/protozero-1.7.0/test/unit/main.cpp:3:
/nvme/rc-buildroot-test/scripts/instance-0/output-1/build/protozero-1.7.0/test/catch/catch.hpp: In member function 'std::string Catch::ExceptionTranslatorRegistrar::ExceptionTranslator<T>::translate(std::vector<std::unique_ptr<const Catch::IExceptionTranslator> >::const_iterator, std::vector<std::unique_ptr<const Catch::IExceptionTranslator> >::const_iterator) const':
/nvme/rc-buildroot-test/scripts/instance-0/output-1/build/protozero-1.7.0/test/catch/catch.hpp:3033:25: error: 'rethrow_exception' is not a member of 'std'
                         std::rethrow_exception(std::current_exception());
                         ^

If we can't disable those tests, what are your suggestion? Should we disable protozero on all those toolchains?