gzdoom: only build for 64-bit architectures #82

Job	Run time
Feeds Package Test Build / Test aarch64_generic	3h 29m 32s
Feeds Package Test Build / Test arm_cortex-a15_neon-vfpv4	2m 26s
Feeds Package Test Build / Test arm_cortex-a9_vfpv3-d16	2m 39s
Feeds Package Test Build / Test i386_pentium-mmx	3m 51s
Feeds Package Test Build / Test mips_24kc	2m 48s
Feeds Package Test Build / Test mipsel_24kc	3m 21s
Feeds Package Test Build / Test powerpc_464fp	2m 47s
Feeds Package Test Build / Test powerpc_8548	2m 36s
Feeds Package Test Build / Test riscv64_riscv64	3h 22m 44s
Feeds Package Test Build / Test x86_64	3h 22m 12s
	10h 34m 56s

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