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.cpp

@@ -28,9 +28,4 @@ __attribute__((noreturn)) void __stack_chk_fail()
     abort();
 }
 
-__attribute__((noreturn)) void __stack_chk_fail_local()
-{
-    __stack_chk_fail();
-}
-
 } // extern "C"