DWARF export creates 64-bit elf files even for 32 bit arch

I'm attempting to export a dwarf file from an ARM:32:LE:Cortex db.

Girdl correctly identifies the arch as 32-bit ARM, but the exporter is hardcoded to produce an ELFCLASS64 file. The ARM machine ID is only valid in ELFCLASS32.

The resulting elf file can't be opened by `arm-none-eabi-gdb`, and if it's opened by `gdb` it's assumed to be X86.