bootstrap: `rustc-args` is only passed to compiletest, not unit tests

[jyn514]

rust/src/bootstrap/test.rs

Line 1586 in 5122e88

flags.extend(builder.config.cmd.rustc_args().iter().map(|s| s.to_string()));

cc https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Running.20tests.20in.20debug.20mode.20with.20debug.20symbols.3F/near/361025470

We should either pass this flag consistently or rip it out entirely; having it work only sometimes makes it an attractive nuisance.

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HEAD is 3307274

[jyn514]

we should at least set them in prepare_cargo_test, probably through RUSTFLAGS since cargo doesn't allow setting them directly?

rust/src/bootstrap/test.rs

Line 2247 in 5122e88

cargo.arg("--").args(&builder.config.test_args()).args(libtest_args);

[chenyukang]

seems we have handled rustc-args for compiletest at here?

rust/src/bootstrap/test.rs

Lines 1595 to 1607 in 5122e88

	let mut hostflags = flags.clone();
	hostflags.push(format!("-Lnative={}", builder.test_helpers_out(compiler.host).display()));
	hostflags.extend(builder.lld_flags(compiler.host));
	for flag in hostflags {
	cmd.arg("--host-rustcflags").arg(flag);
	}
	let mut targetflags = flags;
	targetflags.push(format!("-Lnative={}", builder.test_helpers_out(target).display()));
	targetflags.extend(builder.lld_flags(target));
	for flag in targetflags {
	cmd.arg("--target-rustcflags").arg(flag);
	}