With Glibc 2.26, and GCC 7.2.0. Here below is the build log (after the original build failed, and built again on the same tree to shorten the build log).

```

[  1%] Built target bmalloc
[  2%] Built target WTF
[  3%] Built target stageSharedScripts
[  3%] Built target LLIntOffsetsExtractor
[ 21%] Built target JavaScriptCore
[ 21%] Built target testb3
[ 21%] Built target jsc
[ 21%] Built target testair
[ 21%] Built target brotli
[ 22%] Built target woff2
[ 24%] Built target ANGLESupport
[ 81%] Built target WebCore
[ 82%] Built target WebCoreTestSupport
[ 82%] Built target gtest
[ 82%] Built target WebKit2-forwarding-headers
[ 82%] Automatic MOC for target WebKit2
[ 82%] Built target WebKit2_autogen
[ 97%] Built target WebKit2
[ 97%] Automatic MOC for target WebKit
[ 97%] Built target WebKit_autogen
[ 97%] Linking CXX shared library ../../lib/libQt5WebKit.so
../../lib/../Source/WebKit2/CMakeFiles/WebKit2.dir/Platform/IPC/Connection.cpp.o: In function `IPC::Connection::createSyncMessageEncoder(IPC::StringReference, IPC::StringReference, unsigned long long, unsigned long long&)':
Connection.cpp.text.ZN3IPC10Connection24createSyncMessageEncoderENS_15StringReferenceES1_yRy+0xbc): undefined reference to `_atomic_fetch_add_8'
../../lib/../Source/WebKit2/CMakeFiles/WebKit2.dir/Platform/IPC/Connection.cpp.o: In function `IPC::Connection::sendMessage(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, unsigned int, bool)':
Connection.cpp.text.ZN3IPC10Connection11sendMessageESt10unique_ptrINS_14MessageEncoderESt14default_deleteIS2_EEjb+0x354): undefined reference to `_atomic_fetch_add_8'
../../lib/../Source/WebKit2/CMakeFiles/WebKit2.dir/Platform/IPC/Connection.cpp.o: In function `IPC::Connection::sendSyncReply(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >)':
Connection.cpp.text.ZN3IPC10Connection13sendSyncReplyESt10unique_ptrINS_14MessageEncoderESt14default_deleteIS2_EE+0x310): undefined reference to `_atomic_fetch_add_8'
../../lib/../Source/WebKit2/CMakeFiles/WebKit2.dir/UIProcess/StatisticsRequest.cpp.o: In function `WebKit::StatisticsRequest::addOutstandingRequest()':
StatisticsRequest.cpp.text.ZN6WebKit17StatisticsRequest21addOutstandingRequestEv+0x68): undefined reference to `_atomic_fetch_add_8'
StatisticsRequest.cpp.text.ZN6WebKit17StatisticsRequest21addOutstandingRequestEv+0x2d0): undefined reference to `_atomic_fetch_add_8'
collect2: error: ld returned 1 exit status
make[2]: *** [Source/WebKit/CMakeFiles/WebKit.dir/build.make:2646: lib/libQt5WebKit.so.5.212.0] Error 1
make[1]: *** [CMakeFiles/Makefile2:1053: Source/WebKit/CMakeFiles/WebKit.dir/all] Error 2
make: *** [Makefile:163: all] Error 2

```