Improve check for in-source build.
Pass compiler values to CI scripts.
Added -pthread compiler flag for Unix builds and changed -lpthread to -pthread.
Merge remote-tracking branch 'upstream/next' into MAID-322_fix_cryptest_with_gcc

Conflicts:
	cmake_modules/standard_flags.cmake
add_gtests.cmake now correctly handles commented-out sections of C++ code.
Fixed typo.
Merge remote-tracking branch 'upstream/next' into MAID-322_fix_cryptest_with_gcc

Conflicts:
	cmake_modules/standard_flags.cmake
Added warning message for missing ccache.
Updated to avoid multiple warnings about ccache in a single CMake run.
Minor style fix.
Removed another instance of '-pthread' being added to Clang linker flags.
Merge pull request #161 from Fraser999/MAID-327_fix_add_gtest

MAID-327: add_gtests.cmake now correctly handles commented-out sections of C++ code
Merge pull request #160 from Fraser999/MAID-322_fix_cryptest_with_gcc

MAID-322: Added -pthread compiler flag for Unix builds and changed -lpthread to -p...
<1> adding return statement to cereal functions because every evaluation of return type as non-void will require an explicit mention of "return <non-void-type", otherwise will be caught as compile error by our build system.
<2> putting a file for boost_optional support from https://github.com/stevehickman/cereal/blob/master/include/cereal/types/boost_optional.hpp
auto modified file
removing stuff from CMakeLists.txt that had been added to get cereal headers listed in the IDE for modification
Applied ${TASK_LABEL} to tests' labels.
Merge pull request #158 from Fraser999/MAID-306

MAID-306: Pass compiler values to CI scripts.
Merge remote-tracking branch 'upstream/next' into MAID-415_handle_task_label
Added TASK_LABEL to global labels for Exper targets.