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

fusl/src/signal/siginterrupt.c

Index: fusl/src/signal/siginterrupt.c
diff --git a/fusl/src/signal/siginterrupt.c b/fusl/src/signal/siginterrupt.c
new file mode 100644
index 0000000000000000000000000000000000000000..70063400325c0f74f82235ffc4b9440dd4e264f2
--- /dev/null
+++ b/fusl/src/signal/siginterrupt.c
@@ -0,0 +1,12 @@
+#include <signal.h>
+
+int siginterrupt(int sig, int flag)
+{
+	struct sigaction sa;
+
+	sigaction(sig, 0, &sa);
+	if (flag) sa.sa_flags &= ~SA_RESTART;
+	else sa.sa_flags |= SA_RESTART;
+
+	return sigaction(sig, &sa, 0);
+}