apphelp: Add a stub for ShimFlushCache.

dlls/apphelp/apphelp.c

@@ -74,3 +74,10 @@ BOOL WINAPI ApphelpCheckShellObject( REFCLSID clsid, BOOL shim, ULONGLONG *flags
     if (flags) *flags = 0;
     return TRUE;
 }
+
+BOOL WINAPI ShimFlushCache( HWND hwnd, HINSTANCE instance, LPCSTR cmdline, int cmd )
+{
+    FIXME("stub: %p %p %s %u\n", hwnd, instance, debugstr_a(cmdline), cmd);
+    SetLastError(ERROR_CALL_NOT_IMPLEMENTED);
+    return TRUE;
+}

dlls/apphelp/apphelp.spec

@@ -164,4 +164,4 @@
 @ stub SetPermLayers
 @ stub ShimDbgPrint
 @ stub ShimDumpCache
-@ stub ShimFlushCache
+@ stdcall ShimFlushCache(ptr ptr str long)