[BOLT][DWARF] Handle zero size DW_TAG_inlined_subroutine

We were resetting DW_AT_low_pc to zero when DW_AT_high_pc was zero, or
DW_AT_low_pc == DW_AT_high_pc. This resulted in LLDB to print error "adding
range [0x0-0x0) which has a base that is less than the function's low PC".

Changed it so that when this case arises we set DW_AT_low_pc to the start
address.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132059