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

fusl/src/stdio/__stdio_exit.c

Index: fusl/src/stdio/__stdio_exit.c
diff --git a/fusl/src/stdio/__stdio_exit.c b/fusl/src/stdio/__stdio_exit.c
new file mode 100644
index 0000000000000000000000000000000000000000..191b4454a48d3ff4258c2cd6dd5d29738d79620e
--- /dev/null
+++ b/fusl/src/stdio/__stdio_exit.c
@@ -0,0 +1,24 @@
+#include "stdio_impl.h"
+
+static FILE *volatile dummy_file = 0;
+weak_alias(dummy_file, __stdin_used);
+weak_alias(dummy_file, __stdout_used);
+weak_alias(dummy_file, __stderr_used);
+
+static void close_file(FILE *f)
+{
+	if (!f) return;
+	FFINALLOCK(f);
+	if (f->wpos > f->wbase) f->write(f, 0, 0);
+	if (f->rpos < f->rend) f->seek(f, f->rpos-f->rend, SEEK_CUR);
+}
+
+void __stdio_exit(void)
+{
+	FILE *f;
+	for (f=*__ofl_lock(); f; f=f->next) close_file(f);
+	close_file(__stdin_used);
+	close_file(__stdout_used);
+}
+
+weak_alias(__stdio_exit, __stdio_exit_needed);