Fix issue 21439: install.sh is disabled for LDC on FreeBSD

[jacob-carlborg]

No description provided.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	21439	major	install.sh is disabled for LDC on FreeBSD

[jacob-carlborg]

@MartinNowak can you please deploy this?

[wilzbach]

Sorry for the slow reaction time to this, but I don't think this is a good idea. If FreeBSD is supported, then it should be added explicitly and with a good error message. Without this explicit check, people using it on other systems will get all kind of hard to understand errors.