xfrpc: fix compilation with GCC14 #20716

Job	Run time
Feeds Package Test Build / Test aarch64_generic	11m 19s
Feeds Package Test Build / Test arm_cortex-a15_neon-vfpv4	11m 34s
Feeds Package Test Build / Test arm_cortex-a9_vfpv3-d16	10m 25s
Feeds Package Test Build / Test i386_pentium-mmx	11m 7s
Feeds Package Test Build / Test mips_24kc	10m 13s
Feeds Package Test Build / Test mipsel_24kc	10m 23s
Feeds Package Test Build / Test powerpc_464fp	10m 20s
Feeds Package Test Build / Test powerpc_8548	10m 24s
Feeds Package Test Build / Test riscv64_riscv64	10m 18s
Feeds Package Test Build / Test x86_64	12m 58s
	1h 49m 1s

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