PCH build fix when building with Clang 12

Clang 12 has added a template parameter as "CALLBACK",
which conflicts with the Windows "CALLBACK" define.

Change-Id: I773899d103dcb1a852b555a1900b2de4acb6d96f
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/fileutils.cpp

@@ -44,6 +44,7 @@
 #endif
 
 #ifdef Q_OS_WIN
+#define CALLBACK WINAPI
 #include <qt_windows.h>
 #include <shlobj.h>
 #endif

src/libs/utils/qtcprocess.cpp

@@ -36,6 +36,7 @@
 #include <QStack>
 
 #ifdef Q_OS_WIN
+#define CALLBACK WINAPI
 #include <qt_windows.h>
 #else
 #include <errno.h>

src/plugins/coreplugin/progressmanager/progressmanager_win.cpp

@@ -41,6 +41,7 @@
 
 // for windows progress bar
 #ifndef __GNUC__
+#    define CALLBACK WINAPI
 #    include <shobjidl.h>
 #endif
 

src/plugins/debugger/registerpostmortemaction.cpp

@@ -31,6 +31,7 @@
 #include <QDir>
 #include <QString>
 
+#define CALLBACK WINAPI
 #include <windows.h>
 #include <objbase.h>
 #include <shellapi.h>

src/shared/qtcreator_pch.h

@@ -50,6 +50,9 @@
 #undef ERROR
 #undef ABSOLUTE
 
+// LLVM 12 comes with CALLBACK as a template argument
+#undef CALLBACK
+
 #define _POSIX_
 #include <limits.h>
 #undef _POSIX_