Tests: Fix ExportImport PCH expectation on Cray Classic compiler

Do not expect PCH-included definitions for this compiler.

Tests/ExportImport/Import/Interface/pch_iface_test.cpp

@@ -3,7 +3,7 @@
 #  ifndef PCH_PCH_H_INCLUDED
 #    error "Expected PCH_PCH_H_INCLUDED."
 #  endif
-#elif defined(__PGIC__) || defined(__ibmxl__)
+#elif defined(__PGIC__) || defined(__ibmxl__) || defined(_CRAYC)
 // No PCH expected but these compilers define macros below.
 #elif defined(__GNUC__) || defined(__clang__) || defined(_INTEL_COMPILER) ||  \
   defined(_MSC_VER)