The Lit in subject fails on z/OS since the input file
`Inputs/split-layout.profdata` is marked as ASCII even though it is
binary and the output file `Output/sample-split-layout.test.tmp-output`
is binary.
This PR removes the diff command which fails because it compares a
binary file and a text file. The rational is that this diff command
seems to be redundant to the `FileCheck` on the next command.
Using the flag `-split_layout` in llvm-profdata merge, the output
profile can write profiles with and without inlined function into two
different extbinary sections (and their FuncOffsetTable too). The
section without inlined functions are marked with `SecFlagFlat` and is
skipped by ThinLTO because it provides no useful info.
The split layout feature was already implemented in SampleProfWriter but
previously there is no way to use it from llvm-profdata.
