Due to the mixed usage of `std::string` objects and C-strings, null terminator
characters sometimes propagate into possible `program::updateBuildLog()`
inputs. In particular, `TranslationOutput::frontendCompilerLog` and
`::backendCompilerLog` get set this way within the `CompilerInterface::build()`
API implementation.
This becomes an issue whenever each of CL -> IR and IR -> ISA compilation steps
emits their warnings and/or errors:
`clGetProgramBuildInfo(..., CL_PROGRAM_BUILD_LOG, ...)` also relies on
`std::string` to C-string conversion, so the output is trimmed at the first
null terminator, i.e. the BE part of the build log simply gets lost.
The change handles possible null terminators within `program::updateBuildLog()`
and adds relevant regression tests.
Related-To: IGC-6509
Signed-off-by: Artem Gindinson <artem.gindinson@intel.com>
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