[flang][runtime] Fixed aarach buildbots after #83169.

Author: vzakhari

flang/include/flang/Common/float128.h

@@ -20,6 +20,8 @@
 #ifndef FORTRAN_COMMON_FLOAT128_H_
 #define FORTRAN_COMMON_FLOAT128_H_
 
+#include <float.h>
+
 #ifdef __cplusplus
 /*
  * libc++ does not fully support __float128 right now, e.g.

flang/runtime/complex-reduction.c

@@ -76,6 +76,7 @@ static long_double_Complex_t CMPLXL(long double r, long double i) {
 #endif
 
 #if LDBL_MANT_DIG == 113 || HAS_FLOAT128
+#ifndef CMPLXF128
 /*
  * GCC 7.4.0 (currently minimum GCC version for llvm builds)
  * supports __builtin_complex. For Clang, require >=12.0.
@@ -95,6 +96,7 @@ static CFloat128ComplexType CMPLXF128(CFloat128Type r, CFloat128Type i) {
 }
 #endif
 #endif
+#endif
 
 /* RTNAME(SumComplex4) calls RTNAME(CppSumComplex4) with the same arguments
  * and converts the members of its C++ complex result to C _Complex.