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

fusl/src/stdio/ftrylockfile.c

Index: fusl/src/stdio/ftrylockfile.c
diff --git a/fusl/src/stdio/ftrylockfile.c b/fusl/src/stdio/ftrylockfile.c
new file mode 100644
index 0000000000000000000000000000000000000000..eb13c839bf818a33a8e54016ae962785f1423726
--- /dev/null
+++ b/fusl/src/stdio/ftrylockfile.c
@@ -0,0 +1,40 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+#include <limits.h>
+
+void __do_orphaned_stdio_locks()
+{
+	FILE *f;
+	for (f=__pthread_self()->stdio_locks; f; f=f->next_locked)
+		a_store(&f->lock, 0x40000000);
+}
+
+void __unlist_locked_file(FILE *f)
+{
+	if (f->lockcount) {
+		if (f->next_locked) f->next_locked->prev_locked = f->prev_locked;
+		if (f->prev_locked) f->prev_locked->next_locked = f->next_locked;
+		else __pthread_self()->stdio_locks = f->next_locked;
+	}
+}
+
+int ftrylockfile(FILE *f)
+{
+	pthread_t self = __pthread_self();
+	int tid = self->tid;
+	if (f->lock == tid) {
+		if (f->lockcount == LONG_MAX)
+			return -1;
+		f->lockcount++;
+		return 0;
+	}
+	if (f->lock < 0) f->lock = 0;
+	if (f->lock || a_cas(&f->lock, 0, tid))
+		return -1;
+	f->lockcount = 1;
+	f->prev_locked = 0;
+	f->next_locked = self->stdio_locks;
+	if (f->next_locked) f->next_locked->prev_locked = f;
+	self->stdio_locks = f;
+	return 0;
+}