configure: Undefine FORTIFY_SOURCE first, then define it
configure: Undefine FORTIFY_SOURCE first, then define it

On my hardened gentoo system _FORTIFY_SOURCE is already defined,
thus it makes sense to undefine it first then define it, not vice
versa.

Signed-off-by: Peter Huewe <014f16385c5a8ff1646b588a3d5169b595c0f10e@gmx.de>

01org/TPM2.0-TSS,01org/tpm2-tss,01org/TPM2.0-TSS,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,01org/tpm2-tss,tpm2-software/tpm2-tss,tpm2-software/tpm2-tss,01org/tpm2-tss,01org/TPM2.0-TSS