Build polly-perf-O3 Failure

[Tim Northover]

Hi Tobias,

> it seems there are possible compile time issues with the cmake builds:
>
> objdump/Release+Asserts/llvm-objdump.o:llvm-objdump.cpp:function main:
> error: undefined reference to 'LLVMInitializeARM64Disassembler'
>         collect2: error: ld returned 1 exit status

Isn't that an autotools one? I think they need to be forced to run
configure after new targets are added. (One of the arm bots suffered
the same fate).

Cheers.

Tim.