Add regression test for save temps ICE on incremental recompile

tests/incremental/save-temps-66367.rs

@@ -0,0 +1,18 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/66367>.
+//!
+//! Adding `-C save-temps` to a follow-up incremental compile used to ICE: the codegen unit was
+//! copied from the incremental cache, and the copy-from-cache path asserted that no bytecode was
+//! wanted. `-C save-temps` wants it, so the assertion fired.
+
+//@ revisions: bpass1 bpass2
+//@ compile-flags: -Z query-dep-graph --crate-type=lib
+//@[bpass2] compile-flags: -C save-temps
+
+#![feature(rustc_attrs)]
+// `-C save-temps` is not part of the incremental command line hash, so the codegen unit is still
+// reused in `bpass2` -- which is the path that used to ICE.
+#![rustc_partition_reused(module = "save_temps_66367", cfg = "bpass2")]
+
+pub fn f() -> u32 {
+    1
+}