Bug 2167220

Currently, ikona is built without default Fedora compiler flags for Rust code (i.e. "-Copt-level=3 -Cdebuginfo=2 -Ccodegen-units=1 -Clink-arg=-Wl,-z,relro -Clink-arg=-Wl,-z,now --cap-lints=warn" on Fedora 37) - essentially, the code is not fully optimized, and does not contain debuginfo or frame pointers.

RUSTFLAGS are the standard environment variable for setting compiler flags for rustc (similar to CFLAGS / CXXFLAGS / LDFLAGS), but they aren't set by default (and not yet included in %set_build_flags, but I've reported an RFE about this).

It appears that the ikona build system hard-codes just `--release` flag for cargo, which only implies `-Copt-level=2`. This results in ikona not having valid debug symbols for its Rust code, its code not being optimized to the same level as other Rust code in Fedora, and it not respecting other flags for better code quality and / or debuggability.

A possible solution might be to export RUSTFLAGS, assuming that the build process honors (and does not override) these settings.

I also noticed that ikona bundles lots of ancient (!) Rust crates, and a three-year-old copy of librsvg2, which strikes me as ... unsafe for an application that possibly handles untrusted input. (The bundled dependencies are also not declared in the .spec file, which also results in it not being included in reports for security issues in that bundled stuff. Oh Well.)

A scan of the vendored crates (with "cargo audit") shows that they are vulnerable to several security issues (most of them "high" or "critical"):

chrono 0.4.10: RUSTSEC-2020-0159 / CVE-2020-26235
crossbeam-deque 0.7.2: RUSTSEC-2021-0093 / CVE-2021-32810
futures-task 0.3.4: RUSTSEC-2020-0060 / CVE-2020-35906 and RUSTSEC-2020-0061 / CVE-2020-35907
futures-util 0.3.4: RUSTSEC-2020-0059 / CVE-2020-35905
generic-array 0.13.2: RUSTSEC-2020-0146 / CVE-2020-36465
nalgebra 0.19.0: RUSTSEC-2021-0070 / CVE-2021-38190
regex 1.3.4: RUSTSEC-2022-0013 / CVE-2022-24713
smallvec 1.2.0: RUSTSEC-2021-0003 / CVE-2021-25900
thread_local 1.0.1: RUSTSEC-2022-0006
time 0.1.42: RUSTSEC-2020-0071 / CVE-2020-26235
yaml_rust 0.3.5: RUSTSEC-2018-0006 / CVE-2018-20993