The `obs-studio` package is not build using correct cmake rpm macro, causing %optflags not to be applied:

cd /home/abuild/rpmbuild/BUILD/obs-studio-29.1.3/build/libobs && /usr/bin/cc -DENABLE_DARRAY_TYPE_TEST -DENABLE_HEVC -DHAVE_OBSCONFIG_H -DIS_LIBOBS -DOBS_INSTALL_PREFIX=\"/usr/\" -DOBS_QT_VERSION=6 -DUSE_XDG -Dlibobs_EXPORTS -I/home/abuild/rpmbuild/BUILD/obs-studio-29.1.3/libobs -I/home/abuild/rpmbuild/BUILD/obs-studio-29.1.3/build/config -I/home/abuild/rpmbuild/BUILD/obs-studio-29.1.3/deps/libcaption -I/home/abuild/rpmbuild/BUILD/obs-studio-29.1.3/deps/uthash -isystem /usr/include/ffmpeg -isystem /usr/include/glib-2.0 -isystem /usr/lib64/glib-2.0/include -isystem /usr/include/libmount -isystem /usr/include/blkid -isystem /usr/include/gio-unix-2.0 -isystem /usr/include/wayland -isystem /usr/include/libxkbcommon -O2 -g -DNDEBUG -std=gnu17 -fPIC -Werror -Wextra -Wvla -Wswitch -Wno-error=switch -Wformat -Wformat-security -Wunused-parameter -Wno-unused-function -Wno-missing-field-initializers -fno-strict-aliasing -Werror-implicit-function-declaration -Wno-missing-braces -Wno-error=maybe-uninitialized -mmmx -msse -msse2 -I/usr/include -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/gio-unix-2.0 -pthread -I/usr/include/wayland -MD -MT libobs/CMakeFiles/libobs.dir/media-io/media-remux.c.o -MF CMakeFiles/libobs.dir/media-io/media-remux.c.o.d -o CMakeFiles/libobs.dir/media-io/media-remux.c.o -c /home/abuild/rpmbuild/BUILD/obs-studio-29.1.3/libobs/media-io/media-remux.c

Since the latest ffmpeg update this has caused FTBFS due to upstream injecting `-Werror` to the fallback CFLAGS.