Always check for __attribute__() in CMake

The CMake compiler checks skip checking for things like __attribute__()
on Windows. Now that Visual Studio can use clang, we should be checking
for this, even on non-MinGW Windows.

config/cmake/ConfigureChecks.cmake

@@ -437,16 +437,14 @@ endif ()
 #-----------------------------------------------------------------------------
 # Check a bunch of other functions
 #-----------------------------------------------------------------------------
-if (MINGW OR NOT WINDOWS)
- foreach (other_test
- HAVE_ATTRIBUTE
- HAVE_BUILTIN_EXPECT
- PTHREAD_BARRIER
- HAVE_SOCKLEN_T
+foreach (other_test
+ HAVE_ATTRIBUTE
+ HAVE_BUILTIN_EXPECT
+ PTHREAD_BARRIER
+ HAVE_SOCKLEN_T
  )
- HDF_FUNCTION_TEST (${other_test})
- endforeach ()
-endif ()
+ HDF_FUNCTION_TEST (${other_test})
+endforeach ()
 
 # ----------------------------------------------------------------------
 # Set the flag to indicate that the machine can handle converting