Added a script to update the test file generated by llvm-mc binary. The
script accepts .s and .txt for asm and dasm.
For mc test I am targetting there is no function name which can be used
as a key, thus no clear mapping between input and output. The script
assumes the test are always line-by-line and it update the output marker
for each test line-by-line.
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Co-authored-by: Alexander Richardson <mail@alexrichardson.me>