chrony: fix build with musl

new file mode 100644
index 000000000000..c927b343f754
@@ -0,0 +1,39 @@
+From 1e64bc4c4379ae3e55be3c518e0e3e22c8c4ae77 Mon Sep 17 00:00:00 2001
+From: Baruch Siach <[email protected]>
+Date: Tue, 14 Nov 2017 13:23:57 +0200
+Subject: [PATCH] ntp: fix build with musl libc
+
+The configure script enables HAVE_LINUX_TIMESTAMPING_OPT_PKTINFO based
+on the existence of struct scm_ts_pktinfo and
+SOF_TIMESTAMPING_OPT_PKTINFO that were introduced in Linux kernel v4.13
+in the linux/net_tstamp.h kernel header. But this feature also requires
+SCM_TIMESTAMPING_PKTINFO that is defined in the socket.h header. musl
+libc provides its own version of socket.h, and as of musl version 1.1.16
+this macro is missing. Define this macro in the code as a temporary
+measure until musl is updated to its latest version.
+
+Signed-off-by: Baruch Siach <[email protected]>
+---
+Upstream status: not upstreamable
+---
+ ntp_io_linux.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/ntp_io_linux.c b/ntp_io_linux.c
+index 00caed06f7ba..2214a6f6f6c5 100644
+--- a/ntp_io_linux.c
++++ b/ntp_io_linux.c
+@@ -574,6 +574,10 @@ extract_udp_data(unsigned char *msg, NTP_Remote_Address *remote_addr, int len)
+ 
+ /* ================================================== */
+ 
++#ifndef SCM_TIMESTAMPING_PKTINFO
++#define SCM_TIMESTAMPING_PKTINFO 58
++#endif
++
+ int
+ NIO_Linux_ProcessMessage(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
+                          NTP_Local_Timestamp *local_ts, struct msghdr *hdr, int length)
+-- 
+2.15.0
+