Test CU directory is the work_dir

Make sure that we don't regress setting of the CU directory to the
working directory.

Author: nagisa

src/test/codegen/debug-compile-unit-path.rs

@@ -0,0 +1,9 @@
+// compile-flags: -g --remap-path-prefix={{cwd}}=/cwd/ --remap-path-prefix={{src-base}}=/base/
+// ignore-tidy-linelength
+//
+// Ensure that we remap the compile unit directory and that we set it to the compilers current
+// working directory and not something else.
+#![crate_type="rlib"]
+
+// CHECK-DAG: [[FILE:![0-9]*]] = !DIFile(filename: "/base/debug-compile-unit-path.rs{{.*}}", directory: "/cwd/")
+// CHECK-DAG: {{![0-9]*}} = distinct !DICompileUnit({{.*}}file: [[FILE]]