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

fusl/src/fenv/__flt_rounds.c

Index: fusl/src/fenv/__flt_rounds.c
diff --git a/fusl/src/fenv/__flt_rounds.c b/fusl/src/fenv/__flt_rounds.c
new file mode 100644
index 0000000000000000000000000000000000000000..ec0b3689e5ca2e093a8bac8608f12889b36f18db
--- /dev/null
+++ b/fusl/src/fenv/__flt_rounds.c
@@ -0,0 +1,19 @@
+#include <float.h>
+#include <fenv.h>
+
+int __flt_rounds()
+{
+	switch (fegetround()) {
+#ifdef FE_TOWARDZERO
+	case FE_TOWARDZERO: return 0;
+#endif
+	case FE_TONEAREST: return 1;
+#ifdef FE_UPWARD
+	case FE_UPWARD: return 2;
+#endif
+#ifdef FE_DOWNWARD
+	case FE_DOWNWARD: return 3;
+#endif
+	}
+	return -1;
+}