Remove -Wno-unknown-pragmas from fusl build

fusl/src/math/ilogbl.c

 #include <limits.h>
 #include "libm.h"
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 int ilogbl(long double x)
 {
         return ilogb(x);
 }
 #elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
 int ilogbl(long double x)
 {
-        #pragma STDC FENV_ACCESS ON
+        PRAGMA_STDC_FENV_ACCESS_ON
         union ldshape u = {x};
         uint64_t m = u.i.m;
         int e = u.i.se & 0x7fff;
 
         if (!e) {
                 if (m == 0) {
                         FORCE_EVAL(0/0.0f);
                         return FP_ILOGB0;
                 }
                 /* subnormal x */
@@ skipping 23 matching lines @@
                 return ilogbl(x) - 120;
         }
         if (e == 0x7fff) {
                 FORCE_EVAL(0/0.0f);
                 u.i.se = 0;
                 return u.f ? FP_ILOGBNAN : INT_MAX;
         }
         return e - 0x3fff;
 }
 #endif