GNU/Linux sed requires \? rather than ?. Just use * instead.

R=rsc, r
CC=golang-dev
https://golang.org/cl/810043

src/pkg/deps.bash

@@ -18,7 +18,7 @@ dirpat=$(echo $dirs | sed 's/ /|/g; s/.*/^(&)$/')
 for dir in $dirs; do (
 	cd $dir || exit 1
 
-	sources=$(sed -n 's/^[ \t]*\([^ \t]*\.go\)[ \t]*\\?[ \t]*$/\1/p' Makefile)
+	sources=$(sed -n 's/^[ \t]*\([^ \t]*\.go\)[ \t]*\\*[ \t]*$/\1/p' Makefile)
 	sources=$(echo $sources | sed 's/\$(GOOS)/'$GOOS'/g')
 	sources=$(echo $sources | sed 's/\$(GOARCH)/'$GOARCH'/g')
 	sources=$(ls $sources 2> /dev/null)  # remove .s, .c, etc.