llvm2.9: remove X86 from LLVM_TARGETS_TO_BUILD

* when building for qemux86* it tries to build X86 twice and fails with:
  | CMake Error at lib/Target/CMakeLists.txt:24 (add_subdirectory):
  |   The binary directory
  |
  |     /home/jenkins/oe/shr-core-branches/shr-core/tmp-eglibc/work/x86_64-oe-linux/llvm2.9/2.9-r2.0/llvm-2.9/build/lib/Target/X86
  |
  |   is already used to build a source directory.  It cannot be used to build
  |   source directory
  |
  |     /home/jenkins/oe/shr-core-branches/shr-core/tmp-eglibc/work/x86_64-oe-linux/llvm2.9/2.9-r2.0/llvm-2.9/lib/Target/X86
  |
  |   Specify a unique binary directory name.

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>