[LyX/master] Fix header.

[Richard Kimberly Heck]

commit 4460df329226ab5e72adab0ff764b7496022bbbd
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Fri Feb 28 23:52:06 2020 -0500

    Fix header.
---
 src/support/Systemcall.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/support/Systemcall.h b/src/support/Systemcall.h
index d3d2189..537a701 100644
--- a/src/support/Systemcall.h
+++ b/src/support/Systemcall.h
@@ -15,7 +15,7 @@
 #ifndef SYSTEMCALL_H
 #define SYSTEMCALL_H
 
-#include <string>
+#include "strfwd.h"
 
 namespace lyx {
 namespace support {