[llvm-objdump] Fix common symbol output on 32 bit platforms

Since https://reviews.llvm.org/D109452 symbol-table.test has
been failing on our Arm32 bots.

https://lab.llvm.org/buildbot/#/builders/171/builds/4201

This is because in that change an implicit widening cast
of the alignment from 32 bit to 64 bit was removed and the
format string expects a 64 bit number.