configs/versal_*: move to external Bootlin stable toolchain

This moves the versal defconfigs to the Bootlin glibc stable external toolchain
as per[1].

[1]: https://elinux.org/Buildroot:DeveloperDaysELCE2024#Rules_for_defconfigs

This patch has been run-tested on the vek280 evaluation board.

Signed-off-by: Neal Frager <neal.frager@amd.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

configs/versal_vck190_defconfig

@@ -1,6 +1,8 @@
 BR2_aarch64=y
 BR2_cortex_a72=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_12=y
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_AARCH64_GLIBC_STABLE=y
 BR2_TOOLCHAIN_BARE_METAL_BUILDROOT=y
 BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH="microblazeel-buildroot-elf"
 BR2_GLOBAL_PATCH_DIR="board/xilinx/patches board/xilinx/linux_6.12/patches"

configs/versal_vek280_defconfig

@@ -1,6 +1,8 @@
 BR2_aarch64=y
 BR2_cortex_a72=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_12=y
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_AARCH64_GLIBC_STABLE=y
 BR2_TOOLCHAIN_BARE_METAL_BUILDROOT=y
 BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH="microblazeel-buildroot-elf"
 BR2_GLOBAL_PATCH_DIR="board/versal/vek280/patches board/xilinx/patches board/xilinx/linux_6.12/patches"

configs/versal_vpk180_defconfig

@@ -1,6 +1,8 @@
 BR2_aarch64=y
 BR2_cortex_a72=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_12=y
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
+BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_AARCH64_GLIBC_STABLE=y
 BR2_TOOLCHAIN_BARE_METAL_BUILDROOT=y
 BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH="microblazeel-buildroot-elf"
 BR2_GLOBAL_PATCH_DIR="board/xilinx/patches board/xilinx/linux_6.12/patches"