Make egrep only set REG_EXTENDED flag.
diff --git a/testsuite/grep/egrep-is-not-case-insensitive b/testsuite/grep/egrep-is-not-case-insensitive
new file mode 100644
index 0000000..f12c54c
--- /dev/null
+++ b/testsuite/grep/egrep-is-not-case-insensitive
@@ -0,0 +1 @@
+test x`echo foo | busybox egrep FOO` = x