[llvm] [llvm-objcopy] Support SREC output format (PR #75874)

[via llvm-commits]

quic-areg wrote:

Thank you for your feedback. 

This functionality was mentioned in[ EuroLLVM 2023](https://discourse.llvm.org/t/llvm-embedded-toolchains-eurollvm-2023-round-table-summary/70700): 

> Support for Motorola srec format (GNU objcopy -O srec) would be useful for some projects wanting to transition from GNU.

SREC is used in our team as an intermediate format while generating memory images. Adding support would help them transition to LLVM.

I have updated the documentation to reflect the new output format.

I also simplified this patch like you suggested. It will only write the header record and ignore any sections.

https://github.com/llvm/llvm-project/pull/75874