See GCC bug 69602: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602
which emits the warning for (errno == EWOULDBLOCK || errno == EAGAIN)
which is the correct way of handling errors as the value of EWOULDBLOCK
and EAGAIN is implementation defined.
Therefore introduce a new macro function PHP_IS_TRANSIENT_ERROR()
which handles the case when EWOULDBLOCK and EAGAIN are identical.
Thanks to @twose for the idea.