serialbox%nvhpc does not compile with `icon/25.2:v1` on santis

[jonasjucker]

The build error is

  >> 234    "/capstor/scratch/cscs/juckerj/spack-c2sm/spack-build_stage/spack-stage-serialbox-2.6.1-l7v2ffryb6hxusj2gdv6ive5hb2sn6se/spac
            k-src/src/serialbox/core/hash/SHA256.cpp", line 31: error: namespace "std" has no member "int32_t"
     235      using word_t = std::int32_t;  // 32-bit word, change to "long" for 16-bit machines