The error is caused by a workaround for UNICOS. The workaround
incorrectly uses the _CRAYC macro to determine if building for
UNICOS. This macro will always be defined for the Cray C and
C++ compiler regardless of the target platform, even when
building for Linux. The correct macro should be _CRAY, which as
per Cray documentation is only defined for UNICOS targeted
builds.