few fixes to rust rustdoc-gui tests on windows

config.example.toml

@@ -250,6 +250,13 @@ changelog-seen = 2
 # target when running tests, otherwise this can be omitted.
 #nodejs = "node"
 
+# The npm executable to use. Note that this is used for rustdoc-gui tests,
+# otherwise this can be omitted.
+#
+# Under Windows this should be `npm.cmd` or path to it (verified on nodejs v18.06), or
+# error will be emitted.
+#npm = "npm"
+
 # Python interpreter to use for various tasks throughout the build, notably
 # rustdoc tests, the lldb python interpreter, and some dist bits and pieces.
 #

src/tools/rustdoc-gui-test/src/main.rs

@@ -20,7 +20,7 @@ fn get_browser_ui_test_version_inner(npm: &Path, global: bool) -> Option<String>
         .unwrap_or(String::new());
     lines
         .lines()
-        .find_map(|l| l.split(':').nth(1)?.strip_prefix("browser-ui-test@"))
+        .find_map(|l| l.rsplit(':').next()?.strip_prefix("browser-ui-test@"))
         .map(|v| v.to_owned())
 }