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

fusl/src/signal/psiginfo.c

Index: fusl/src/signal/psiginfo.c
diff --git a/fusl/src/signal/psiginfo.c b/fusl/src/signal/psiginfo.c
new file mode 100644
index 0000000000000000000000000000000000000000..57be34cd017ca4041f7cb2029e825ad45e796cd7
--- /dev/null
+++ b/fusl/src/signal/psiginfo.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+
+void psiginfo(const siginfo_t *si, const char *msg)
+{
+	char *s = strsignal(si->si_signo);
+	if (msg) fprintf(stderr, "%s: %s\n", msg, s);
+	else fprintf(stderr, "%s\n", s);
+}