Got these errors while cross-compiling for Linux from Windows:
non-portable path to file '"logging/LogMacros.h"'; specified path differs in case from file name on disk -Werror,-Wnonportable-include-path] \Engine\Source\Runtime\Core\Public\Serialization\BufferWriter.h 11
non-portable path to file '"json.h"'; specified path differs in case from file name on disk -Werror,-Wnonportable-include-path] \Engine\Source\Runtime\Slate\Public\SlateBasics.h 11
Fixed that by modifying LinuxToolChain in our engine build - just added -Wno-nonportable-include-path flag. Maybe it would be useful to someone. Also, Epic should probably fix it.