Fix clang-10 compilation issue (#839) clang-10 throws the following error: In file included from external/org_brotli/c/enc/bit_cost.c:9: external/org_brotli/c/enc/./bit_cost.h:48:16: error: implicit conversion from 'size_t' (aka 'unsigned long') to 'double' may lose precision [-Werror,-Wimplicit-int-float-conversion] if (retval < sum) { ~ ^~~ 1 error generated. Make the conversion explicit.