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

fusl/src/math/lrint.c

+#include <limits.h>
+#include <fenv.h>
+#include "libm.h"
+
+/*
+If the result cannot be represented (overflow, nan), then
+lrint raises the invalid exception.
+
+Otherwise if the input was not an integer then the inexact
+exception is raised.
+
+C99 is a bit vague about whether inexact exception is
+allowed to be raised when invalid is raised.
+(F.9 explicitly allows spurious inexact exceptions, F.9.6.5
+does not make it clear if that rule applies to lrint, but
+IEEE 754r 7.8 seems to forbid spurious inexact exception in
+the ineger conversion functions)
+
+So we try to make sure that no spurious inexact exception is
+raised in case of an overflow.
+
+If the bit size of long > precision of double, then there
+cannot be inexact rounding in case the result overflows,
+otherwise LONG_MAX and LONG_MIN can be represented exactly
+as a double.
+*/
+
+#if LONG_MAX < 1U<<53 && defined(FE_INEXACT)
+long lrint(double x)
+{
+        #pragma STDC FENV_ACCESS ON
+        int e;
+
+        e = fetestexcept(FE_INEXACT);
+        x = rint(x);
+        if (!e && (x > LONG_MAX || x < LONG_MIN))
+                feclearexcept(FE_INEXACT);
+        /* conversion */
+        return x;
+}
+#else
+long lrint(double x)
+{
+        return rint(x);
+}
+#endif