Update Kokkos library in LAMMPS to v3.4.0

lib/kokkos/cmake/compile_tests/cplusplus14.cpp

@@ -0,0 +1,8 @@
+#include <type_traits>
+
+int main() {
+  // _t versions of type traits were added in C++14
+  std::remove_cv_t<int> i = 0;
+
+  return i;
+}

lib/kokkos/cmake/compile_tests/cuda_compute_capability.cc

@@ -72,6 +72,7 @@ int main() {
     case 72: std::cout << "Set -DKokkos_ARCH_VOLTA72=ON ." << std::endl; break;
     case 75: std::cout << "Set -DKokkos_ARCH_TURING75=ON ." << std::endl; break;
     case 80: std::cout << "Set -DKokkos_ARCH_AMPERE80=ON ." << std::endl; break;
+    case 86: std::cout << "Set -DKokkos_ARCH_AMPERE86=ON ." << std::endl; break;
     default:
       std::cout << "Compute capability " << compute_capability
                 << " is not supported" << std::endl;

lib/kokkos/cmake/compile_tests/pthread.cpp

@@ -2,7 +2,7 @@
 
 void* kokkos_test(void* args) { return args; }
 
-int main(void) {
+int main() {
   pthread_t thread;
   /* Use NULL to avoid C++11. Some compilers
      do not have C++11 by default.  Forcing C++11