Extend QNX support by adding all currently supported variants

[darkwisebear]

Add support for QNX8 by introducing a version constraint that allows for the selection of the respective ABI target of the Rust compiler. Since QNX also supports dylibs, also include the nto system as dylib supporting platform.

In addition, also add all supported targets to the list of Tier 3 architectures. Since cargo-bazel also needs to know the additional triples, it's version of cfg-expr needs to be bumped.

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