Bug 2167235

Currently, the Rust code in kata-containers 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 kata-containers Makfiles currently hard-codes only the "--release" flag for cargo (which is equivalent to `-Copt-level=2`).

This results in Rust code which is compiled as part of kata-containers not being optimized at the same level as other Rust code in Fedora (i.e. `-Copt-level=3` is default in Fedora), it doesn't get debug symbols (missing `-Cdebuginfo=2` flag, which is non-standard for `--release` mode), and it also doesn't include the other mandatory compiler flags, which result in better quality of generated code (`-Ccodegen-units=1`), and on rawhide, includes frame pointers on x86_64 and aarch64.

Usually exporting  RUSTFLAGS="%build_rustflags" environment variable in such cases should be enough, but looking at the Makefiles in kata-containers, they seem to override this variable whether it was set in the environment or not ... so fixing this problem might involve patching some Makefiles.