Icecream 1.3 and Icemon 3.3 released

A new version 1.3 of the distributed C/C++ compilation tool Icecream has been released. To accompany it, version 3.3 of the GUI monitor Icemon has been released as well.

The changelogs are here and here. In a less changelog-y way, the changes are:

• Compiler location are no longer hardcoded anywhere. Previously the compiler automatically packaged and sent to remote nodes was always /usr/bin/gcc (g++, clang, clang++). That might not match the actual compiler used and the workaround was to manually package the proper one using icecc-create-env. But now it's possible to build even with e.g. CXX=/my/own/build/of/clang and it'll simply work. This should also mean that explicitly setting $ICECC_VERSION now should be needed only for cross-compiling.
• Slightly better job scheduling, both for remote and local builds. For example, the local machine should no longer be possibly overloaded by running way too many local preprocessor steps.
• Better compression, both for sending data and packaged compilers. Compilation data is compressed using zstd if the other node supports it, compiler environments can be compiled using zstd or xz. This improves performance by reducing both network and CPU usage. Note that while compilation compression falls back to the older method if not supported by the other side, for compiler environments this is more tricky and so it has to be set up manually. You can set e.g. ICECC_ENV_COMPRESSION=xz , but the daemon will not fall back to using any other mechanism. Which means it will use only nodes that are at least version 1.3, the scheduler should also be from 1.3 (run another one if needed, the newest one wins) and the remote node needs to support the compression (1.3 uses newly uses libarchive, which supports zstd only in its relatively recent releases). So this is mainly useful if you have full control over the Icecream cluster, but by default the compression is the old gzip, for backwards compatibility.
• Speaking of which, the maximum cache size for compiler environments now defaults to 256MiB. Use the --cache-size option of iceccd for different sizes.
• Objective C/C++ support has been fixed.
• Some special workarounds for GCC's -fdirectives-only option that is used when sending sources to remote nodes, as it breaks in some corner cases.
• The --interface option of the daemons (and scheduler) now allow binding only to a specific network interface, if needed. Note that Icecream still assumes it runs in a trusted network and if that's not so it's up to you to ensure it by using tools such as a firewall.
• Icemon now displays in the defailed host view what protocol a node supports (1.3 has protocol version 42, env_xz/env_zstd mean it supports compiler environments compiled using xz/zstd).
• And various other fixes.