linux-user: Assert stack used for auxvec, envp, argv

Assert that the amount of stack space used for auxvec, envp & argv
exactly matches the amount allocated. This catches if DLINFO_ITEMS isn't
updated when another NEW_AUX_ENT is added.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Riku Voipio <riku.voipio@iki.fi>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

linux-user/elfload.c

@@ -1455,6 +1455,8 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
     info->auxv_len = sp_auxv - sp;
 
     sp = loader_build_argptr(envc, argc, sp, p, 0);
+    /* Check the right amount of stack was allocated for auxvec, envp & argv. */
+    assert(sp_auxv - sp == size);
     return sp;
 }