I thought it would be a good idea to upgrade my offline signer to a current version. But I had to build from source because I need a 32bit executable (old Pentium M)

Compilation on 32bit x86 showed an error which was already reported for 0.95 - but the OP failed to respond to Goatpig's question about the build environment.
Check my response in that thread https://bitcointalk.org/index.php?topic=1657365.msg20477795#msg20477795 if you run into compile error on "non standard" hardware.