Mitigate relocation overflow [part 2 of 2]

_init_array_start/end are placed at 0 if no ".init_array" presents,
this causes .text relocation against them become more prone to overflow.
This CL sets ".init_array" address to that of ".text" to mitigate the situation.

Review: https://reviews.llvm.org/D46200
llvm-svn: 332688