Fixes for busybox

--- a/tests/status-detached.expected
+++ b/tests/status-detached.expected
@@ -1 +1 @@
-nanosleep\({tv_sec=2, tv_nsec=0},  <detached \.\.\.>
+nanosleep\(\{tv_sec=2, tv_nsec=0\},  <detached \.\.\.>
--- a/tests/strace--tips.test
+++ b/tests/strace--tips.test
@@ -13,7 +13,7 @@ tips_fmt_opt=""
 
 grep_ere_escape()
 {
-	printf "%s" "$*" | sed 's/[].*&^$()|[\/]/\\&/g'
+	printf "%s" "$*" | sed 's/[].*&^$(){}|[\\/]/\\&/g'
 }
 
 # Check that simple "strace --tips=0" works as expected
--- a/tests/strace-k.test
+++ b/tests/strace-k.test
@@ -26,10 +26,9 @@ check_prog sed
 check_prog tr
 
 path_to_sed="$(command -v sed)"
-if [ -x "$path_to_sed" ] &&
-   path_to_sed="$(readlink -ev -- "$path_to_sed")"; then
+if [ -x "$path_to_sed" ]; then
 	"$path_to_sed" -n 's/^[^/]\+[[:space:]]\(\/.*\)$/\1/p' /proc/self/maps |
-	grep -F -x -e "$path_to_sed" > /dev/null || {
+	grep -F -x -e "$(readlink -fv -- "$path_to_sed")" > /dev/null || {
 		cat >&2 /proc/self/maps
 		framework_skip_ '/proc/self/maps is invalid'
 	}