bring back temporarily disabled `-Werror` (_POSIX_C_SOURCE, _XOPEN_SOURCE redefined with Python 3.15)

[slayoo]

The warning was disabled after Python 3.15 started to trigger the following errors on Ubuntu:

            /usr/bin/g++ -D_header_self_contained__tmp_pip_req_build__3ojqv9o_src_aero_binned_hpp -I/tmp/_build/include -I/tmp/pip-req-build-_3ojqv9o/gitmodules/json/include -I/tmp/pip-req-build-_3ojqv9o/gitmodules/nanobind/include -I/tmp/pip-req-build-_3ojqv9o/gitmodules/nanobind_json/include -I/tmp/pip-req-build-_3ojqv9o/gitmodules/span/include -I/tmp/pip-req-build-_3ojqv9o/gitmodules/string_view-standalone/include -I/tmp/pip-req-build-_3ojqv9o/gitmodules/optional/include -I/opt/hostedtoolcache/Python/3.15.0-rc.2/x64/include/python3.15 -Werror -std=c++17 -fPIE -o CMakeFiles/cmTC_54cf9.dir/src.cxx.o -c /tmp/_build/CMakeFiles/CMakeScratch/TryCompile-qCUKmT/src.cxx
            In file included from /opt/hostedtoolcache/Python/3.15.0-rc.2/x64/include/python3.15/Python.h:14,
                             from /tmp/pip-req-build-_3ojqv9o/gitmodules/nanobind/include/nanobind/nb_python.h:21,
                             from /tmp/pip-req-build-_3ojqv9o/gitmodules/nanobind/include/nanobind/nanobind.h:32,
                             from /tmp/pip-req-build-_3ojqv9o/src/aero_data.hpp:14,
                             from /tmp/pip-req-build-_3ojqv9o/src/aero_binned.hpp:10,
                             from /tmp/_build/CMakeFiles/CMakeScratch/TryCompile-qCUKmT/src.cxx:6:
            /opt/hostedtoolcache/Python/3.15.0-rc.2/x64/include/python3.15/pyconfig.h:2067: error: "_POSIX_C_SOURCE" redefined [-Werror]
             2067 | #define _POSIX_C_SOURCE 202405L
                  |
            In file included from /usr/include/x86_64-linux-gnu/c++/13/bits/os_defines.h:39,
                             from /usr/include/x86_64-linux-gnu/c++/13/bits/c++config.h:679,
                             from /usr/include/c++/13/bits/requires_hosted.h:31,
                             from /usr/include/c++/13/iostream:38,
                             from /tmp/pip-req-build-_3ojqv9o/src/pmc_resource.hpp:9,
                             from /tmp/pip-req-build-_3ojqv9o/src/aero_binned.hpp:9:
            /usr/include/features.h:292: note: this is the location of the previous definition
              292 | # define _POSIX_C_SOURCE        200809L
                  |
            /opt/hostedtoolcache/Python/3.15.0-rc.2/x64/include/python3.15/pyconfig.h:2124: error: "_XOPEN_SOURCE" redefined [-Werror]
             2124 | #define _XOPEN_SOURCE 800
                  |
            /usr/include/features.h:216: note: this is the location of the previous definition
              216 | # define _XOPEN_SOURCE  700
                  |
            cc1plus: all warnings being treated as errors
            ninja: build stopped: subcommand failed.

          exitCode: 1