Patch D80794 remove the custom flags for release build for flang.

This leads to build failure with GCC < 8. This patch add upperbound check

in order to avoid the -Werror=array-bounds to trigger a build failure.

/home/4vn/versioning/llvm-project/flang/lib/Decimal/big-radix-floating-point.h:183:29: error: array subscript is above array bounds [-Werror=array-bounds] digit_[j] = digit_[j + remove]; ~~~~~~^ /home/4vn/versioning/llvm-project/flang/lib/Decimal/big-radix-floating-point.h:183:29: error: array subscript is above array bounds [-Werror=array-bounds] digit_[j] = digit_[j + remove]; ~~~~~~^ /home/4vn/versioning/llvm-project/flang/lib/Decimal/big-radix-floating-point.h:183:29: error: array subscript is above array bounds [-Werror=array-bounds] digit_[j] = digit_[j + remove]; ~~~~~~^ /home/4vn/versioning/llvm-project/flang/lib/Decimal/big-radix-floating-point.h:183:29: error: array subscript is above array bounds [-Werror=array-bounds] digit_[j] = digit_[j + remove]; ~~~~~~^ /home/4vn/versioning/llvm-project/flang/lib/Decimal/big-radix-floating-point.h:183:29: error: array subscript is above array bounds [-Werror=array-bounds] digit_[j] = digit_[j + remove];

/home/4vn/versioning/llvm-project/flang/include/flang/Evaluate/integer.h:809:28: error: array subscript is above array bounds [-Werror=array-bounds] xy += product[to]; ~~~~~~~^ /home/4vn/versioning/llvm-project/flang/include/flang/Evaluate/integer.h:810:22: error: array subscript is above array bounds [-Werror=array-bounds] product[to] = xy & partMask; ~~~~~~~^ /home/4vn/versioning/llvm-project/flang/include/flang/Evaluate/integer.h:809:28: error: array subscript is above array bounds [-Werror=array-bounds] xy += product[to]; ~~~~~~~^