x86/purgatory: Remove -nostdlib compiler flag

x86/purgatory: Remove -nostdlib compiler flag

The -nostdlib option requests the compiler to not use the standard
system startup files or libraries when linking. It is effective only
when $(CC) is used as a linker driver.

$(LD) is directly used for linking purgatory.{ro,chk} here, hence
-nostdlib is unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20211107162641.324688-2-masahiroy@kernel.org