Tests: Build automatically, fix compilation errors

Tests/Kernel/null-deref-crash-during-pthread_join.cpp

@@ -1,21 +0,0 @@
-#include <pthread.h>
-#include <stdio.h>
-#include <sys/select.h>
-#include <unistd.h>
-
-int main(int, char**)
-{
-    pthread_t tid;
-    pthread_create(
-        &tid, nullptr, [](void*) -> void* {
-            sleep(1);
-            asm volatile("ud2");
-            return nullptr;
-        },
-        nullptr);
-
-    pthread_join(tid, nullptr);
-
-    printf("ok\n");
-    return 0;
-}