Hardened versions of gcc default to building position-independent
code, which breaks our i386 build.  Our build process therefore
detects such platforms and automatically adds "-fno-PIE -nopie" to the
gcc command line.

On x86_64, we choose to build position-independent code (in order to
reduce the final binary size and, in particular, the number of
relocations required for UEFI binaries).  The workaround therefore
breaks the build process for x86_64 binaries on such platforms.

Fix by moving the workaround to the i386-specific portion of the
Makefile.

Reported-by: Jan Kundrát <jkt@kde.org>
Debugged-by: Jan Kundrát <jkt@kde.org>
Debugged-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>