adjust tests to leave lld in beta

- stable tests to ensure lld is not used
- splitting beta (where lld is on) behavior from stable (where it is
  off)

Author: lqd

tests/run-make/rust-lld-by-default-stable/main.rs

@@ -0,0 +1 @@
+fn main() {}

tests/run-make/rust-lld-by-default-stable/rmake.rs

@@ -0,0 +1,13 @@
+// Ensure that rust-lld is *not* used as the default linker on `x86_64-unknown-linux-gnu` on stable.
+
+//@ only-stable
+//@ only-x86_64-unknown-linux-gnu
+
+use run_make_support::linker::assert_rustc_doesnt_use_lld;
+use run_make_support::rustc;
+
+fn main() {
+    // A regular compilation should not use rust-lld by default. We'll check that by asking the
+    // linker to display its version number with a link-arg.
+    assert_rustc_doesnt_use_lld(rustc().input("main.rs"));
+}

tests/run-make/rust-lld-x86_64-unknown-linux-gnu-dist/rmake.rs

@@ -1,7 +1,8 @@
-// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu`
-// dist artifacts and that it can also be turned off with a CLI flag.
+// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu` dist artifacts
+// (except on stable) and that it can also be turned off with a CLI flag.
 
 //@ only-dist
+//@ ignore-stable
 //@ only-x86_64-unknown-linux-gnu
 
 use run_make_support::linker::{assert_rustc_doesnt_use_lld, assert_rustc_uses_lld};

tests/run-make/rust-lld-x86_64-unknown-linux-gnu/rmake.rs

@@ -1,11 +1,12 @@
-// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu`
-// and that it can also be turned off with a CLI flag.
+// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu` (except on
+// stable) and that it can also be turned off with a CLI flag.
 //
 // This version of the test checks that LLD is used by default when LLD is enabled in the
 // toolchain. There is a separate test that checks that LLD is used for dist artifacts
 // unconditionally.
 
 //@ needs-rust-lld
+//@ ignore-stable
 //@ only-x86_64-unknown-linux-gnu
 
 use run_make_support::linker::{assert_rustc_doesnt_use_lld, assert_rustc_uses_lld};