x86/build changes for v6.10:

 - Use -fpic to build the kexec 'purgatory' (self-contained code that runs between two kernels)

 - Clean up vmlinux.lds.S generation

 - Simplify the X86_EXTENDED_PLATFORM section of the x86 Kconfig

 - Misc cleanups & fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>