Kernel: Disable __thread and TLS on x86_64 for now

They're not yet properly supported.

Userland/Libraries/LibC/pthread_tls.cpp

@@ -26,7 +26,10 @@ struct SpecificTable {
 
 static KeyTable s_keys;
 
-__thread SpecificTable t_specifics;
+#    ifndef X86_64_NO_TLS
+__thread
+#    endif
+    SpecificTable t_specifics;
 
 int __pthread_key_create(pthread_key_t* key, KeyDestructor destructor)
 {

Userland/Libraries/LibDl/dlfcn.cpp

@@ -11,8 +11,16 @@
 #include <string.h>
 
 // FIXME: use thread_local and a String once TLS works
-__thread char* s_dlerror_text = NULL;
-__thread bool s_dlerror_retrieved = false;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    char* s_dlerror_text
+    = NULL;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    bool s_dlerror_retrieved
+    = false;
 
 static void store_error(const String& error)
 {

Userland/Libraries/LibPthread/pthread.cpp

@@ -33,8 +33,14 @@ static constexpr size_t required_stack_alignment = 4 * MiB;
 static constexpr size_t highest_reasonable_guard_size = 32 * PAGE_SIZE;
 static constexpr size_t highest_reasonable_stack_size = 8 * MiB; // That's the default in Ubuntu?
 
-__thread void* s_stack_location;
-__thread size_t s_stack_size;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    void* s_stack_location;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    size_t s_stack_size;
 
 #define __RETURN_PTHREAD_ERROR(rc) \
     return ((rc) < 0 ? -(rc) : 0)