ShellCommand: Add missing include

It was included only by another included header.

Change-Id: Idff745a7d811c7fe0c4c791eeda884bcd4a62d98
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/utils/shellcommand.cpp

@@ -26,6 +26,7 @@
 #include "shellcommand.h"
 
 #include "fileutils.h"
+#include "qtcassert.h"
 #include "synchronousprocess.h"
 #include "runextensions.h"