rustc: rename -Z emit-directives to -Z emit-artifact-notifications and simplify the output.

src/test/ui/emit-artifact-notifications.nll.stderr

@@ -0,0 +1 @@
+{"artifact":"$TEST_BUILD_DIR/emit-artifact-notifications.nll/libemit_artifact_notifications.rmeta"}

src/test/ui/emit-artifact-notifications.rs

@@ -0,0 +1,6 @@
+// compile-flags:--emit=metadata --error-format=json -Z emit-artifact-notifications
+// compile-pass
+
+// A very basic test for the emission of artifact notifications in JSON output.
+
+fn main() {}

src/test/ui/emit-artifact-notifications.stderr

@@ -0,0 +1 @@
+{"artifact":"$TEST_BUILD_DIR/emit-artifact-notifications/libemit_artifact_notifications.rmeta"}

src/test/ui/emit-directives.rs

@@ -1,6 +0,0 @@
-// compile-flags:--emit=metadata --error-format=json -Z emit-directives
-// compile-pass
-
-// A very basic test for the emission of build directives in JSON output.
-
-fn main() {}

src/test/ui/emit-directives.stderr

@@ -1 +0,0 @@
-{"directive":"metadata file written: $TEST_BUILD_DIR/emit-directives/libemit_directives.rmeta"}