With gcc (GCC) 7.2.1 20170915 (Red Hat 7.2.1-2) (fedora 27)

int main(int argc, char **argv) {
  int k = 0x7fffffff;
  k += argc;
  return 0;
}

$ clang -static -fsanitize=undefined test.c

vs

$ gcc -static -fsanitize=undefined test.c
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_linux_libcdep.o): In function `__sanitizer::GetThreadStackTopAndBottom(bool, unsigned long*, unsigned long*)':
(.text+0x551): undefined reference to `pthread_attr_init'
(.text+0x556): undefined reference to `pthread_self'
(.text+0x561): undefined reference to `pthread_getattr_np'
(.text+0x599): undefined reference to `pthread_attr_destroy'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_linux_libcdep.o): In function `__sanitizer::SetEnv(char const*, char const*)':
(.text+0x70b): undefined reference to `dlsym'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_linux_libcdep.o): In function `__sanitizer::InitTlsSize()':
(.text+0x843): undefined reference to `dlsym'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_posix_libcdep.o): In function `__sanitizer::GetNamedMappingFd(char const*, unsigned long)':
(.text+0x747): undefined reference to `shm_open'
(.text+0x763): undefined reference to `shm_unlink'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_posix_libcdep.o): In function `__sanitizer::AdjustStackSize(void*)':
(.text+0xa8f): undefined reference to `pthread_attr_setstacksize'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_posix_libcdep.o): In function `__sanitizer::GetThreadSelf()':
(.text+0x1d1): undefined reference to `pthread_self'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_posix_libcdep.o): In function `__sanitizer::my_pthread_attr_getstack(void*, void**, unsigned long*)':
(.text+0x9b1): undefined reference to `pthread_attr_getstack'
/usr/lib/gcc/x86_64-redhat-linux/7/libubsan.a(sanitizer_symbolizer_posix_libcdep.o): In function `__sanitizer::Symbolizer::LateInitialize()':
(.text+0x7e3): undefined reference to `dlsym'
collect2: error: ld returned 1 exit status