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

fusl/src/complex/cacoshl.c

Index: fusl/src/complex/cacoshl.c
diff --git a/fusl/src/complex/cacoshl.c b/fusl/src/complex/cacoshl.c
new file mode 100644
index 0000000000000000000000000000000000000000..65342557f9a545ef935190b3c64b6bdf2c6ceaa5
--- /dev/null
+++ b/fusl/src/complex/cacoshl.c
@@ -0,0 +1,14 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double complex cacoshl(long double complex z)
+{
+	return cacosh(z);
+}
+#else
+long double complex cacoshl(long double complex z)
+{
+	z = cacosl(z);
+	return CMPLXL(-cimagl(z), creall(z));
+}
+#endif