To build on Ubuntu-18.04 I need to add this: ``` -------------------- bootstrap/stage0/runtime/AK/Format.cpp -------------------- index 43b125cb..58ac662a 100644 @@ -34,6 +34,11 @@ # include <AK/StringFloatingPointConversions.h> #endif +#if defined(AK_OS_LINUX) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 30 +#include <sys/syscall.h> +#define gettid() syscall(SYS_gettid) +#endif + namespace AK { namespace { ``` Edited to add check for `AK_OS_LINUX`.