configs/beaglebone: Switch to Bootlin glibc stable toolchain

Switch to Bootlin glibc stable toolchain as requested by the 2024
Buildroot meeting report:
https://elinux.org/Buildroot:DeveloperDaysELCE2024#Rules_for_defconfigs

Signed-off-by: Kory Maincent (TI.com) <kory.maincent@bootlin.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

configs/beaglebone_defconfig

@@ -1,7 +1,9 @@
 BR2_arm=y
 BR2_cortex_a8=y
 BR2_ARM_FPU_VFPV3=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_12=y
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_ARMV7_EABIHF_GLIBC_STABLE=y
 BR2_GLOBAL_PATCH_DIR="board/beagleboard/beaglebone/patches"
 BR2_DOWNLOAD_FORCE_CHECK_HASHES=y
 BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV=y