Remove -Wno-unknown-pragmas from fusl build

fusl/src/math/ilogb.c

 #include <limits.h>
 #include "libm.h"
 
 int ilogb(double x)
 {
-        #pragma STDC FENV_ACCESS ON
+        PRAGMA_STDC_FENV_ACCESS_ON
         union {double f; uint64_t i;} u = {x};
         uint64_t i = u.i;
         int e = i>>52 & 0x7ff;
 
         if (!e) {
                 i <<= 12;
                 if (i == 0) {
                         FORCE_EVAL(0/0.0f);
                         return FP_ILOGB0;
                 }
                 /* subnormal x */
                 for (e = -0x3ff; i>>63 == 0; e--, i<<=1);
                 return e;
         }
         if (e == 0x7ff) {
                 FORCE_EVAL(0/0.0f);
                 return i<<12 ? FP_ILOGBNAN : INT_MAX;
         }
         return e - 0x3ff;
 }