Add -Wno-write-strings

This is being turned on in the main repo.

Change-Id: I76206922c4db10e4572541a8c442c4ba7bbdaf43
diff --git a/embdrv/sbc/BUILD.gn b/embdrv/sbc/BUILD.gn
index 653037a..90f66b1 100644
--- a/embdrv/sbc/BUILD.gn
+++ b/embdrv/sbc/BUILD.gn
@@ -22,6 +22,7 @@
   cflags = [
     "-Wno-conversion",
     "-Wno-implicit-fallthrough",
+    "-Wno-write-strings",
   ]
 }