Remove -Wno-unknown-pragmas from fusl build

fusl/src/math/llrintl.c

 #include <limits.h>
 #include <fenv.h>
 #include "libm.h"
 
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 long long llrintl(long double x)
 {
         return llrint(x);
 }
 #elif defined(FE_INEXACT)
 /*
 see comments in lrint.c
 
 Note that if LLONG_MAX == 0x7fffffffffffffff && LDBL_MANT_DIG == 64
 then x == 2**63 - 0.5 is the only input that overflows and
 raises inexact (with tonearest or upward rounding mode)
 */
 long long llrintl(long double x)
 {
-        #pragma STDC FENV_ACCESS ON
+        PRAGMA_STDC_FENV_ACCESS_ON
         int e;
 
         e = fetestexcept(FE_INEXACT);
         x = rintl(x);
         if (!e && (x > LLONG_MAX || x < LLONG_MIN))
                 feclearexcept(FE_INEXACT);
         /* conversion */
         return x;
 }
 #else
 long long llrintl(long double x)
 {
         return rintl(x);
 }
 #endif