LibC: Properly implement stack protectors

The shared parts are now firmly compiled into LibC instead of being
defined as a static library and then being copied over manually.
The non-shared ("local") parts are kept as a static library that is
linked into each binary on demand.

This finally allows us to support linking with the -fstack-protector
flag, which now replaces the `ssp` target being linked into each binary
accidentally via CMake.

Userland/Libraries/LibC/ssp_nonshared.cpp

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2021, Brian Gianforcaro <bgianf@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/internals.h>
+
+#if defined __SSP__ || defined __SSP_ALL__
+#    error "file must not be compiled with stack protection enabled on it. Use -fno-stack-protector"
+#endif
+
+extern "C" {
+
+__attribute__((noreturn)) void __stack_chk_fail_local()
+{
+    __stack_chk_fail();
+}
+
+} // extern "C"