Log an error when endianness change is not compatible with arch

[wargio]

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Detailed description

This generates a log when the switch to a specific endianness fails.

[0x00000000]> e asm.arch=x86
[0x00000000]> e cfg.bigendian
false
[0x00000000]> e cfg.bigendian=true
ERROR: core: cannot change to big endian (arch 'x86' supports only little endian)
[0x00000000]> e asm.arch=sysz 
[0x00000000]> e cfg.bigendian
true
[0x00000000]> e cfg.bigendian=false
ERROR: core: cannot change to little endian (arch 'sysz' supports only big endian)

[wargio]

The issue is when setting the default endianness, i forgot to change that :D