Change in flashrom[master]: spi: Define _XOPEN_SOURCE to get ffs() from strings.h

[Septs (Code Review)]

Hello build bot (Jenkins), Nico Huber, Paul Menzel,

I'd like you to do a code review. Please visit

https://review.coreboot.org/c/flashrom/+/46512

to review the following change.

Change subject: spi: Define _XOPEN_SOURCE to get ffs() from strings.h
......................................................................

spi: Define _XOPEN_SOURCE to get ffs() from strings.h

Fixes build with Musl libc.

Change-Id: I92b69300a302c4491e234666ac371027571801c9
Signed-off-by: Nico Huber 
Reviewed-on: https://review.coreboot.org/22951
Tested-by: build bot (Jenkins) 
Reviewed-by: Paul Menzel 
Reviewed-by: David Hendricks 
---
M spi.c
1 file changed, 2 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/12/46512/1

diff --git a/spi.c b/spi.c
index aed2a92..f124533 100644
--- a/spi.c
+++ b/spi.c
@@ -18,6 +18,8 @@
  * Contains the generic SPI framework
  */

+#define _XOPEN_SOURCE 700	/* for ffs() */
+
 #include <strings.h>
 #include <string.h>
 #include "flash.h"