Add regression test for rust-lang#69264

Author: GuillaumeGomez

tests/rustdoc-ui/remap-path-prefix-lint.rs

@@ -0,0 +1,10 @@
+// Regression test for remapped paths in rustdoc errors
+// <https://github.com/rust-lang/rust/issues/69264>.
+
+//@ compile-flags:-Z unstable-options --remap-path-prefix={{src-base}}=remapped_path
+//@ rustc-env:RUST_BACKTRACE=0
+
+#![deny(rustdoc::invalid_html_tags)]
+
+/// </script>
+pub struct Bar;

tests/rustdoc-ui/remap-path-prefix-lint.stderr

@@ -0,0 +1,14 @@
+error: unopened HTML tag `script`
+  --> remapped_path/remap-path-prefix-lint.rs:9:5
+   |
+LL | /// </script>
+   |     ^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> remapped_path/remap-path-prefix-lint.rs:7:9
+   |
+LL | #![deny(rustdoc::invalid_html_tags)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+