fix(SConscript): use build_env instead of env in loop

[rosacry]

Summary

Fixes a bug in the libsafety SConscript where the loop variable build_env is ignored, causing both regular and mutation testing builds to use the same environment.

The Bug

The loop iterates with build_env alternating between env and menv, but the body always uses env:

for build_env, suffix in ((env, ""), (menv, "_mutation")):
    safety = env.SharedObject(...)    # Always uses `env`
    libsafety = env.SharedLibrary(...)

This means libsafety_mutation.so should use menv (clang-17, Mull plugin, coverage flags) but incorrectly uses env.

The Fix

Use the loop variable build_env instead of hardcoded env:

safety = build_env.SharedObject(f"safety{suffix}.os", "safety.c")
libsafety = build_env.SharedLibrary(f"libsafety{suffix}", [safety])

Files Changed

• opendbc/safety/tests/libsafety/SConscript - Use build_env instead of env in loop body

[Copilot]

Pull request overview

This PR fixes a bug in the libsafety SConscript build configuration where the loop variable build_env was being ignored, causing both the regular and mutation testing builds to incorrectly use the same environment (env) instead of their respective environments.

Key Changes:

• Use build_env instead of hardcoded env in SharedObject and SharedLibrary calls within the build loop
• Remove hardcoded .so extension from SharedLibrary call (SCons adds platform-appropriate extension automatically)

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[Copilot]

The SideEffect declaration still uses env and is inside the loop, which causes issues. On the second loop iteration when build_env == menv, the safety variable refers to the mutation build object, but this line declares that the GCC coverage file safety.gcno is a side effect of it, which is incorrect since the mutation build uses clang-17 and won't generate .gcno files. This should either be moved outside the loop after the loop completes, or be conditional on build_env == env, or use build_env if both environments can generate side effect files that need cleaning.

Suggested change

	env.SideEffect("safety.gcno", safety)
	if build_env == env:
	build_env.SideEffect("safety.gcno", safety)

[rosacry]

What looked like a bug was actually working code with implicit CI dependencies. My bad.