389-ds-base does not honor standard Fedora compiler flags for Rust

[vashirov]

Issue Description Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=2167213

Currently, the Rust module in 389-ds-base 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") - 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 389-ds-base build system currently hard-codes these compiler flags: --release --verbose -- -C debuginfo=2

This results in Rust code compiled as part of 389-ds-base not being optimized at the same level as other Rust code in Fedora (i.e. -Copt-level=3 is default in Fedora, but --release mode only implies -Copt-level=2), and it also doesn't include the other mandatory compiler flags, which result in better quality of generated code (and on rawhide, includes frame pointers on x86_64 and aarch64).

[Firstyear]

https://doc.rust-lang.org/cargo/reference/profiles.html#opt-level

"It is recommended to experiment with different levels to find the right balance for your project. There may be surprising results, such as level 3 being slower than 2, or the "s" and "z" levels not being necessarily smaller. "

It's not wise to apply blanket settings from the distro, they may not always be correct.

[decathorpe]

It's not wise to apply blanket settings from the distro, they may not always be correct.

At least in Fedora, default compiler flags MUST be honored unless there is a documented reason not to do so.