[ELF] - Recommit "[ELF] - Do not forget to fill last bytes of PT_LOADs with trap instructions."

With fix: explicitly specify ouput format for hexdump tool call.

Original commit message:

[ELF] - Do not forget to fill last bytes of PT_LOADs with trap instructions.

Previously last 4 bytes of executable loads
were not filled with trap instructions,
patch fixes this bug.

Differential revision: https://reviews.llvm.org/D36262

llvm-svn: 311315