Simplify Travis-CI FreeBSD build

[nurupo]

I went ahead and updated FreeBSD to use 11.2 image because the 11.1 was giving

WARNING: FreeBSD 11.1-RELEASE is approaching its End-of-Life date.
It is strongly recommended that you upgrade to a newer
release within the next 2 months.

message. I had to reduce the 8 mirrors down to 2, because apparently only 2 of them have 11.2 release. They must be syncing once per month or rarer. We could add more mirrors as more of them get the release.

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This change is 

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[nurupo]

Here is the build https://travis-ci.org/TokTok/c-toxcore/builds/402243877.

[iphydf]

Reviewable status: 0 of 1 LGTMs obtained (waiting on @iphydf)

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.travis/cmake-freebsd-stage2, line 18 at r1 (raw file):

  # Extract the cached image
  tar -Sxzvf $IMAGE_NAME.tgz

Put variables into double quotes to avoid potential double parsing of values with spaces in them.

[nurupo]

Hm, the build suddenly started failing, it wasn't doing that before. poweroff as root disconnects us from ssh but for some reason the VM still keeps running until the build times out, it doesn't "poweroff" properly.

[nurupo]

Sending poweroff over ssh doesn't work but sending it to the qemu tty does. Go figure what the issue is. I would have tried to reproduce the ssh poweroff issue on my local machine, but I have 4GiB of disk space left which won't be enough. Sending poweroff to tty works and I don't see any downsides to it, do let's just roll with that.

[nurupo]

Reviewed 6 of 9 files at r1, 4 of 4 files at r2.
Reviewable status: 0 of 1 LGTMs obtained

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.travis/cmake-freebsd-stage2, line 18 at r1 (raw file):

Previously, iphydf wrote…

Put variables into double quotes to avoid potential double parsing of values with spaces in them.

Done.

[nurupo]

Reviewable status: 0 of 1 LGTMs obtained

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.travis/cmake-freebsd-stage1, line 0 at r2 (raw file):

File appears to be binary.

Good job reviewable.

[iphydf]

Reviewable status: 0 of 1 LGTMs obtained

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.travis/cmake-freebsd-stage1, line at r2 (raw file):

Previously, nurupo wrote…

File appears to be binary.

Good job reviewable.

It's because there is a literal ESC byte in this script instead of an escape sequence for it.

[iphydf]

Reviewable status: complete! 1 of 1 LGTMs obtained

[nurupo]

Reviewable status: complete! 1 of 1 LGTMs obtained

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.travis/cmake-freebsd-stage1, line at r2 (raw file):

Previously, iphydf wrote…

It's because there is a literal ESC byte in this script instead of an escape sequence for it.

That was my guess.

[nurupo]

Rebased on master.