[vte/vte-0-64] build: Fix build on non-linux systems

[Christian Persch <chpe src gnome org>]

commit 0e069018082d9736e15fe8ba93a47a0f4a787e39
Author: Brad Smith <brad comstyle com>
Date:   Sun Jun 27 12:17:08 2021 +0200

    build: Fix build on non-linux systems
    
    Fixes: https://gitlab.gnome.org/GNOME/vte/-/issues/2501
    (cherry picked from commit 674f864269d0842376752487f29bfdddc8c7ec9f)

 src/missing.hh | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/missing.hh b/src/missing.hh
index 80ffe355..e5a58727 100644
--- a/src/missing.hh
+++ b/src/missing.hh
@@ -21,11 +21,14 @@
 
 #include <csignal>
 #include <fcntl.h>
+
+#ifdef __linux__
 #include <sys/syscall.h>
 
 #if defined(__mips__) || defined(__mips64__)
 #include <asm/sgidefs.h>
 #endif
+#endif
 
 /* NSIG isn't in POSIX, so if it doesn't exist use this here. See bug #759196 */
 #ifndef NSIG