Add a "fork" of musl as //fusl.

fusl/src/unistd/pipe2.c

Index: fusl/src/unistd/pipe2.c
diff --git a/fusl/src/unistd/pipe2.c b/fusl/src/unistd/pipe2.c
new file mode 100644
index 0000000000000000000000000000000000000000..f24f74fb0300d0d1cfe40e93d1da24b63be081f4
--- /dev/null
+++ b/fusl/src/unistd/pipe2.c
@@ -0,0 +1,22 @@
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include "syscall.h"
+
+int pipe2(int fd[2], int flag)
+{
+	if (!flag) return pipe(fd);
+	int ret = __syscall(SYS_pipe2, fd, flag);
+	if (ret != -ENOSYS) return __syscall_ret(ret);
+	ret = pipe(fd);
+	if (ret) return ret;
+	if (flag & O_CLOEXEC) {
+		__syscall(SYS_fcntl, fd[0], F_SETFD, FD_CLOEXEC);
+		__syscall(SYS_fcntl, fd[1], F_SETFD, FD_CLOEXEC);
+	}
+	if (flag & O_NONBLOCK) {
+		__syscall(SYS_fcntl, fd[0], F_SETFL, O_NONBLOCK);
+		__syscall(SYS_fcntl, fd[1], F_SETFL, O_NONBLOCK);
+	}
+	return 0;
+}