Work around missing standard pre-defined macros

When compiling with emscripten em++ FE_INEXACT and __STDC_IEC_559__ are
not defined.

ChangeLog:

	* testsuite/tests/math_1arg.cc: Without FE_INEXACT float
	exceptions are not test anyway. Just #ifdef the code.
	* testsuite/tests/operators.cc: If neither __GCC_IEC_559 nor
	__STDC_IEC_559__ are defined assume no IEC60559 compliance.

testsuite/tests/math_1arg.cc

@@ -92,8 +92,11 @@ template <typename V>
 		   MAKE_TESTER(lgamma), MAKE_TESTER(nearbyint), MAKE_TESTER(rint),
 		   MAKE_TESTER(lrint), MAKE_TESTER(llrint), MAKE_TESTER(ilogb));
 
+
+#ifdef FE_INEXACT
     FloatExceptCompare::ignore_spurious = FE_INEXACT;
     FloatExceptCompare::ignore_missing = FE_INEXACT;
+#endif
 
     test_values<V>(input_values, {10000}, MAKE_TESTER(ceil), MAKE_TESTER(floor), MAKE_TESTER(trunc),
 		   MAKE_TESTER(round), MAKE_TESTER(lround), MAKE_TESTER(llround));

testsuite/tests/operators.cc

@@ -214,8 +214,10 @@ template <typename V>
     constexpr bool is_iec559 =
 #ifdef __GCC_IEC_559
       __GCC_IEC_559 >= 2;
-#else
+#elif defined __STDC_IEC_559__
       __STDC_IEC_559__ == 1;
+#else
+      false;
 #endif
     if constexpr (std::is_floating_point_v<T> && !is_iec559)
       { // avoid testing subnormals and expect minor deltas for non-IEC559 float