CMake: print the bit representation of the test number

I need this to investigate why the test is failing in Travis CI.

CMakeLists.txt

@@ -56,8 +56,10 @@ option(ENABLE_LIBPNG "Enable support for writing png files (screenshots, images)
 option(ENABLE_HISTORY "Enable using GNU history for history in lua console" ON)
 
 if(NOT CMAKE_CROSSCOMPILING)
-	try_run(IEEE754_TEST_RETURN_CODE IEEE754_TEST_COMPILED ${CMAKE_BINARY_DIR} ${CMAKE_SOURCE_DIR}/src/compile_time_tests/ieee_754.cpp)
+	try_run(IEEE754_TEST_RETURN_CODE IEEE754_TEST_COMPILED ${CMAKE_BINARY_DIR} ${CMAKE_SOURCE_DIR}/src/compile_time_tests/ieee_754.cpp
+		RUN_OUTPUT_VARIABLE IEEE754_TEST_OUTPUT)
 	if(NOT IEEE754_TEST_RETURN_CODE EQUAL 0)
+		message(${IEEE754_TEST_OUTPUT})
 		message(FATAL_ERROR "Your platform does not represent floating point numbers in the IEEE 754 format.")
 	endif()
 else()

src/compile_time_tests/ieee_754.cpp

@@ -1,4 +1,6 @@
+#include <cinttypes>
 #include <cstdint>
+#include <cstdio>
 
 // This test verifies that floating point numbers are represented in the IEEE 754 format.
 // Wesnoth requires that.
@@ -11,7 +13,13 @@ int main()
 	} number;
 
 	number.floating_point_number = 1.2;
+	bool match = (number.integer == 0x3FF3333333333333ull);
+	if (!match)
+	{
+		std::printf("Wrong binary representation. Expected 0x3FF3333333333333, got 0x%" PRIX64 "\n",
+		            number.integer);
+	}
 	// Return code zero means success.
 	// Thus, check that the bit representation is *not* what IEEE 754 specifies.
-	return number.integer != 0x3FF3333333333333ull;
+	return !match;
 }