[compiler-rt] Add more diagnostic to InstrProfError

[compiler-rt] Add more diagnostic to InstrProfError

If profile data is malformed for any kind of reason, we generate
an error that only reports "malformed instrumentation profile data"
without any further information. This patch extends InstrProfError
class to receive an optional error message argument, so that we can
do better error reporting.

Differential Revision: https://reviews.llvm.org/D108942