[BOLT] Add writable segment for allocatable sections

The golang support creates 2 new data segments, one of them contains
relocations in PIC binaries, so the section must have writable rights.
Currently BOLT creates only one new segment that contains new sections
with RX rights, now also create RW segment if there are any new writable
sections were allocated during BOLT binary processing.

Vladislav Khmelevsky,
Advanced Software Technology Lab, Huawei

Differential Revision: https://reviews.llvm.org/D143390