Make `mach test-unit` not recompile components after `mach build`

Previously, the `tests` feature flag of the `embedder_traits` crate
caused it and every crate recursively depending on it to be built twice.

This feature flag was used to provide a specific set of "resources"
when running tests. Instead, this commits overrides the `main()` function
of the test harness to change resources at runtime before running any test.

This is done by adding a dependency that has `name = "test"` in its
`[lib]` section of `Cargo.toml`. This overrides the crate found by
`extern crate test;` in code generated by `rustc --test`.

1 files changed, 15 insertions, 0 deletions

diff --git a/components/std_test_override/lib.rs b/components/std_test_override/lib.rs
new file mode 100644
index 00000000000..8d38f6835e5
--- /dev/null
+++ b/components/std_test_override/lib.rs
@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![feature(test)]
+
+extern crate embedder_traits;
+extern crate test;
+
+pub use test::*;
+
+pub fn test_main_static(tests: &[&TestDescAndFn]) {
+    embedder_traits::resources::set_for_tests();
+    test::test_main_static(tests);
+}