devel/qcoro: fix build on powerpc*

Fixed in LLVM 16:
fatal error: error in backend: failed to perform tail call elimination on a call site marked musttail
PLEASE submit a bug report to https://bugs.freebsd.org/submit/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.	Program arguments: /usr/bin/c++ -DQT_CORE_LIB -DQT_NO_CAST_FROM_ASCII -DQT_NO_CAST_FROM_BYTEARRAY -DQT_NO_CAST_TO_ASCII -DQT_NO_DEBUG -DQT_NO_FOREACH -DQT_NO_KEYWORDS -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_NO_URL_CAST_FROM_STRING -DQT_STRICT_ITERATORS -DQT_TESTCASE_BUILDDIR=\"/wrkdirs/usr/ports/devel/qcoro/work-qt5/.build\" -DQT_TESTLIB_LIB -DQT_USE_STRINGBUILDER -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/.build/tests/test-qcorosignal_autogen/include -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0/tests/testlibs -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0 -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0/qcoro -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0/qcoro/core -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/.build/qcoro/core -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/.build/qcoro -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0/qcoro/test -I/wrkdirs/usr/ports/devel/qcoro/work-qt5/.build/qcoro/test -isystem /usr/local/include/qt5 -isystem /usr/local/include/qt5/QtCore -isystem /usr/local/lib/qt5/mkspecs/freebsd-clang -isystem /usr/local/include/qt5/QtTest -O2 -pipe -fstack-protector-strong -fno-strict-aliasing -fcoroutines-ts -O2 -pipe -fstack-protector-strong -fno-strict-aliasing -DNDEBUG -std=gnu++20 -fPIC -pthread -MD -MT tests/CMakeFiles/test-qcorosignal.dir/qcorosignal.cpp.o -MF tests/CMakeFiles/test-qcorosignal.dir/qcorosignal.cpp.o.d -o tests/CMakeFiles/test-qcorosignal.dir/qcorosignal.cpp.o -c /wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0/tests/qcorosignal.cpp
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '/wrkdirs/usr/ports/devel/qcoro/work-qt5/qcoro-0.9.0/tests/qcorosignal.cpp'.
4.	Running pass 'PowerPC DAG->DAG Pattern Instruction Selection' on function '@_ZZ19qCoroSignalListenerI15MultiSignalTestM10SignalTestFvvEEN5QCoro14AsyncGeneratorINS4_6detail16QCoroSignalQueueIT_T0_E11result_type10value_typeEEEPS8_OS9_NSt3__16chrono8durationIxNSF_5ratioILl1ELl1000EEEEEENKUlNSF_10unique_ptrINS7_IS0_S3_EENSF_14default_deleteISM_EEEEE_clESP_.resume'
 #0 0x0000000014b1252c (/usr/bin/c+++0x14b1252c)
 #1 0x0000000014b0fd00 (/usr/bin/c+++0x14b0fd00)
 #2 0x0000000014aab0cc (/usr/bin/c+++0x14aab0cc)
 #3 0x0000000014aab020 (/usr/bin/c+++0x14aab020)
 #4 0x0000000014afc590 (/usr/bin/c+++0x14afc590)
 #5 0x00000000117cd530 (/usr/bin/c+++0x117cd530)
 #6 0x0000000014ab4fe0 (/usr/bin/c+++0x14ab4fe0)
 #7 0x0000000014ab4e6c (/usr/bin/c+++0x14ab4e6c)
 #8 0x00000000154bd3f0 (/usr/bin/c+++0x154bd3f0)
 #9 0x0000000014d5f9d0 (/usr/bin/c+++0x14d5f9d0)
c++: error: clang frontend command failed with exit code 70 (use -v to see invocation)
FreeBSD clang version 14.0.5 (https://github.com/llvm/llvm-project.git llvmorg-14.0.5-0-gc12386ae247c)
Target: powerpc64le-unknown-freebsd13.2
Thread model: posix
InstalledDir: /usr/bin
c++: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
c++: note: diagnostic msg: /tmp/qcorosignal-479743.cpp
c++: note: diagnostic msg: /tmp/qcorosignal-479743.sh
c++: note: diagnostic msg:

********************

devel/qcoro/Makefile

@@ -27,4 +27,11 @@ CMAKE_ARGS=	-DUSE_QT_VERSION=${FLAVOR:S/qt//}
 
 PLIST_SUB=	QT_VER=${FLAVOR:S/qt//}
 
+.include <bsd.port.options.mk>
+
+.if ${ARCH:Mpowerpc*}
+CXX=		clang++${LLVM_VERSION}
+USES+=		llvm:min=16
+.endif
+
 .include <bsd.port.mk>