fix msvc build

error C2039: 'isspace': is not a member of 'std'

Change-Id: I92410b09c4de18d9c3c43a2f052a6b2595c92013
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/projectexplorer/projectmacro.cpp

@@ -26,6 +26,7 @@
 #include "projectmacro.h"
 
 #include <utils/algorithm.h>
+#include <cctype>
 
 namespace ProjectExplorer {