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

fusl/src/signal/sigandset.c

Index: fusl/src/signal/sigandset.c
diff --git a/fusl/src/signal/sigandset.c b/fusl/src/signal/sigandset.c
new file mode 100644
index 0000000000000000000000000000000000000000..974186f3d034bf3c77d70ccec6657fd558f2eaf5
--- /dev/null
+++ b/fusl/src/signal/sigandset.c
@@ -0,0 +1,12 @@
+#define _GNU_SOURCE
+#include <signal.h>
+
+#define SST_SIZE (_NSIG/8/sizeof(long))
+
+int sigandset(sigset_t *dest, const sigset_t *left, const sigset_t *right)
+{
+	unsigned long i = 0, *d = (void*) dest, *l = (void*) left, *r = (void*) right;
+	for(; i < SST_SIZE; i++) d[i] = l[i] & r[i];
+	return 0;
+}
+