[C++] Handle multi-word SHELL in $(shell)
diff --git a/strutil.h b/strutil.h
index 5938efb..12e46a5 100644
--- a/strutil.h
+++ b/strutil.h
@@ -142,4 +142,6 @@
 
 string EchoEscape(const string str);
 
+void EscapeShell(string* s);
+
 #endif  // STRUTIL_H_