Fix llvm-gcc bootstrap with gnu ld.

Fix llvm-gcc bootstrap with gnu ld.
The problem was codegen guessing the wrong values and printing

	.section	.eh_frame,"aMS",@progbits,4

It is not clear at all if Codegen should try to guess, MC is the
one that should know the default flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126421 91177308-0d34-0410-b5e6-96231b3b80d8