Revert "Add fix for O_NONBLOCK file-descriptor as output pipe"

This reverts commit be8f7d1716.

This was reverted as with this commit the program would consume large amounts
of cpu time just looping and calling the write function, which would not block.

shadermeh.c

@@ -51,7 +51,7 @@ static int write_retry(int fd, const void *buffer, size_t size)
 		int ret = write(fd, buffer, size);
 
 		if (ret < 0) {
-			if (errno == EINTR || errno == EAGAIN)
+			if (errno == EINTR)
 				continue;
 			perror("write");
 			return -1;