[U-Boot] [u-boot][coreboot-x86] Incremental Make fails

[Hua Yanghao]

Hi,
When doing make for coreboot-x86, in arch/x86/lib/Makefile it
re-generates libgcc.a from the original toolchain libgcc.a and did
some patching for certain libgcc functions. And this seems having some
issues when you try to do incremental compilation.

Steps to reproduce the issue:
1. Setup toolchain
2. make coreboot-x86 # sucess for the first time
3. make # second make fails with message:
make[1]: Entering directory `/home/hua/git/u-boot/arch/x86/lib'
make[1]: *** No rule to make target `.depend', needed by `built-in.o'.  Stop.
make[1]: Leaving directory `/home/hua/git/u-boot/arch/x86/lib'

Can anyone give some hints in how to solve this issue?

Regards,
Yanghao