Improve support for sourcemapped-stacktrace within a single combined script file

Added a end of line match character when looking for the `sourceMappedURL` comment in a script file.

This will allow `sourcemapped-stacktrace.js` itself to be combined into a single script file (along with other application code).

Without this character, the regex will find the match string in the source code of `sourcemapped-stacktrace.js` itself that is combined with other scripts rather than the actual comment generated at the end of the combined script file.