[Tests] Output of od can be lower or upper case (llvm-objcopy/yaml2obj).
The command od -t x is used to dump data in hex format.
The LIT tests assumes that the hex characters are in lowercase.
However, there are also platforms which use uppercase letter.
To solve this issue the tests are updated to use the new
--ignore-case option of FileCheck.
Reviewers: Bigcheese, jakehehrlich, rupprecht, espindola, alexshap, jhenderson
Differential Revision: https://reviews.llvm.org/D68693