Update version to 2.5.2-dev #640

Job	Run time
Buildroot (qemu_x86_defconfig, glibc)	1m 27s
Buildroot (qemu_x86_defconfig, uclibc)	1m 38s
Buildroot (qemu_x86_defconfig, musl)	1m 23s
Buildroot (qemu_x86_64_defconfig, glibc)	1m 27s
Buildroot (qemu_x86_64_defconfig, uclibc)	1m 22s
Buildroot (qemu_x86_64_defconfig, musl)	1m 22s
Buildroot (raspberrypi4_defconfig, glibc)	1m 30s
Buildroot (raspberrypi4_defconfig, uclibc)	1m 43s
Buildroot (raspberrypi4_defconfig, musl)	2m 14s
Buildroot (raspberrypi4_64_defconfig, glibc)	2m 16s
Buildroot (raspberrypi4_64_defconfig, uclibc)	1m 25s
Buildroot (raspberrypi4_64_defconfig, musl)	2m 11s
Buildroot (qemu_ppc64le_pseries_defconfig, glibc)	2m 17s
Buildroot (qemu_ppc64le_pseries_defconfig, uclibc)	1m 27s
Buildroot (qemu_ppc64le_pseries_defconfig, musl)	2m 8s
Buildroot (qemu_mips32r2_malta_defconfig, glibc)	1m 26s
Buildroot (qemu_mips32r2_malta_defconfig, uclibc)	1m 20s
Buildroot (qemu_mips32r2_malta_defconfig, musl)	1m 19s
Buildroot (qemu_mips64_malta_defconfig, glibc)	2m 15s
Buildroot (qemu_mips64_malta_defconfig, uclibc)	2m 5s
Buildroot (qemu_mips64_malta_defconfig, musl)	2m 5s
Buildroot (qemu_riscv32_virt_defconfig, glibc)	1m 24s
Buildroot (qemu_riscv32_virt_defconfig, uclibc)	2m 25s
Buildroot (qemu_riscv32_virt_defconfig, musl)	2m 10s
Buildroot (qemu_riscv64_virt_defconfig, glibc)	1m 28s
Buildroot (qemu_riscv64_virt_defconfig, uclibc)	1m 19s
Buildroot (qemu_riscv64_virt_defconfig, musl)	1m 22s
	46m 28s

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