Description of problem:
Package obs-studio fails to build from source in Fedora Rawhide.

Version-Release number of selected component (if applicable):
31.1.1-3.fc44

Steps to Reproduce:
koji build --scratch f44 obs-studio-31.1.1-3.fc44.src.rpm

Additional info:
This package is tracked by Koschei. See:
https://koschei.fedoraproject.org/package/obs-studio

Build started failing here: https://koschei.fedoraproject.org/build/21601793 .
Compiler errors:
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp: In function ‘void PopulateBitrateLists()’:
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:131:16: error: reference to ‘once_flag’ is ambiguous
  131 |         static once_flag once;
      |                ^~~~~~~~~
In file included from /builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:6:
/usr/include/c++/15/mutex:809:10: note: candidates are: ‘struct std::once_flag’
  809 |   struct once_flag
      |          ^~~~~~~~~
In file included from /usr/include/stdlib.h:1162,
                 from /usr/include/c++/15/cstdlib:83,
                 from /usr/include/c++/15/ext/string_conversions.h:45,
                 from /usr/include/c++/15/bits/basic_string.h:4444,
                 from /usr/include/c++/15/string:56,
                 from /builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.hpp:4,
                 from /builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:1:
/usr/include/bits/types/once_flag.h:24:21: note:                 ‘typedef struct __once_flag once_flag’
   24 | typedef __once_flag once_flag;
      |                     ^~~~~~~~~
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:133:19: error: ‘once’ was not declared in this scope
  133 |         call_once(once, []() {
      |                   ^~~~
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp: In function ‘void PopulateSimpleAACBitrateMap()’:
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:188:16: error: reference to ‘once_flag’ is ambiguous
  188 |         static once_flag once;
      |                ^~~~~~~~~
/usr/include/c++/15/mutex:809:10: note: candidates are: ‘struct std::once_flag’
  809 |   struct once_flag
      |          ^~~~~~~~~
/usr/include/bits/types/once_flag.h:24:21: note:                 ‘typedef struct __once_flag once_flag’
   24 | typedef __once_flag once_flag;
      |                     ^~~~~~~~~
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:190:19: error: ‘once’ was not declared in this scope
  190 |         call_once(once, []() {
      |                   ^~~~
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp: In function ‘void PopulateSimpleOpusBitrateMap()’:
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:257:16: error: reference to ‘once_flag’ is ambiguous
  257 |         static once_flag once;
      |                ^~~~~~~~~
/usr/include/c++/15/mutex:809:10: note: candidates are: ‘struct std::once_flag’
  809 |   struct once_flag
      |          ^~~~~~~~~
/usr/include/bits/types/once_flag.h:24:21: note:                 ‘typedef struct __once_flag once_flag’
   24 | typedef __once_flag once_flag;
      |                     ^~~~~~~~~
/builddir/build/BUILD/obs-studio-31.1.1-build/obs-studio-31.1.1/frontend/utility/audio-encoders.cpp:259:19: error: ‘once’ was not declared in this scope
  259 |         call_once(once, []() {
      |                   ^~~~