Fix nightlies -- workaround compiler bug in GCC 9.1 and 9.2 (kokkos#6118

)

* Workaround compiler bug in GCC 9.1 and 9.2

* KOKKOS_COMPILER_GCC -> KOKKOS_COMPILER_GNU

Co-authored-by: Daniel Arndt <arndtd@ornl.gov>

* Update guards to use the workaround for GCC 9.0.1 as well

Co-authored-by: Nathan Ellingwood <ndellin@sandia.gov>

* Update comment to reflect more accurately what was done

---------

Co-authored-by: Daniel Arndt <arndtd@ornl.gov>
Co-authored-by: Nathan Ellingwood <ndellin@sandia.gov>

core/unit_test/TestBitManipulationBuiltins.hpp

@@ -789,7 +789,14 @@ struct TestBitCastFunction {
     ASSERT_EQ(errors, 0) << "Failed check no error for bit_cast()";
   }
   template <typename To, typename From>
-  static KOKKOS_FUNCTION bool check(const From& from) {
+#if defined(KOKKOS_COMPILER_GNU) && (900 <= KOKKOS_COMPILER_GNU) && \
+    (KOKKOS_COMPILER_GNU < 930)
+  // workaround compiler bug seen in GCC 9.0.1 and GCC 9.2.0
+  KOKKOS_FUNCTION bool check(const From& from) const
+#else
+  static KOKKOS_FUNCTION bool check(const From& from)
+#endif
+  {
     using Kokkos::Experimental::bit_cast_builtin;
     return bit_cast_builtin<From>(bit_cast_builtin<To>(from)) == from;
   }