x11-wm/hyprland: unbreak build with GCC after 33b9f9f8

FAILED: src/Hyprland
/usr/local/bin/ld: src/Hyprland.p/managers_ThreadManager.cpp.o: in function `std::__1::basic_filebuf<char, std::__1::char_traits<char> >::overflow(int)':
ThreadManager.cpp:(.text._ZNSt3__113basic_filebufIcNS_11char_traitsIcEEE8overflowEi[_ZNSt3__113basic_filebufIcNS_11char_traitsIcEEE8overflowEi]+0x2e4): undefined reference to `std::bad_cast::bad_cast()'
/usr/local/bin/ld: src/Hyprland.p/managers_ThreadManager.cpp.o: in function `std::__1::basic_filebuf<char, std::__1::char_traits<char> >::sync()':
ThreadManager.cpp:(.text._ZNSt3__113basic_filebufIcNS_11char_traitsIcEEE4syncEv[_ZNSt3__113basic_filebufIcNS_11char_traitsIcEEE4syncEv]+0x306): undefined reference to `std::bad_cast::bad_cast()'
/usr/local/bin/ld: src/Hyprland.p/managers_ThreadManager.cpp.o: in function `std::__1::basic_filebuf<char, std::__1::char_traits<char> >::seekoff(long long, std::__1::ios_base::seekdir, unsigned int)':
ThreadManager.cpp:(.text._ZNSt3__113basic_filebufIcNS_11char_traitsIcEEE7seekoffExNS_8ios_base7seekdirEj[_ZNSt3__113basic_filebufIcNS_11char_traitsIcEEE7seekoffExNS_8ios_base7seekdirEj]+0x166): undefined reference to `std::bad_cast::bad_cast()'
[...]

x11-wm/hyprland/Makefile

@@ -58,6 +58,7 @@ post-install:
 .endif
 
 # XXX Drop after FreeBSD 13.2 EOL around 2024-05-01 (don't forget distinfo)
+.if ${CXX} == c++ && exists(/usr/lib/libc++.so)
 .if !exists(/usr/include/c++/v1/__ranges/as_rvalue_view.h) || make(makesum) || make(fetch)
 . if exists(/usr/include/c++/v1/__algorithm/ranges_all_of.h) && !make(makesum) && !make(fetch)
 CXXFLAGS+=	-fexperimental-library # std::ranges::all_of
@@ -86,5 +87,6 @@ bundled-libcxx:
 	@${DO_MAKE_BUILD:NDESTDIR*} install -C ${WRKDIR}/libcxx_build
 . endif
 .endif
+.endif # exists(/usr/lib/libc++.so)
 
 .include <bsd.port.mk>