Hide the usage of `rb_io_t` where possible. (#7880)

This retries the compatible parts of the previously reverted PR so we can continue to update related code without breaking backwards compatibility.

1 files changed, 1 insertions, 0 deletions

diff --git a/process.c b/process.c
index c54e11860e..b4435446f0 100644
--- a/process.c
+++ b/process.c
@@ -103,6 +103,7 @@ int initgroups(const char *, rb_gid_t);
 #include "internal/error.h"
 #include "internal/eval.h"
 #include "internal/hash.h"
+#include "internal/io.h"
 #include "internal/numeric.h"
 #include "internal/object.h"
 #include "internal/process.h"