Optimize the build error report of "Build failed, do you want to continue?"

[testforstephen]

Customer verbatim:
"the java debugger extentions sometimes gives errors but there is not any errors"
"Sometimes it gets debugger errors"
"Everything is good but when we run the code it have a problem it shows first run the code. Please fix it then it will run the code."

[testforstephen]

Thoughts:
When checking the build errors, we could filter the irrevelant errors.

1. For multi-module projects, only report the errors in the classpath of the running project.
2. Exclude the errors from the test scope if running a normal application.
3. For unmanaged folder, only report the error from the main class.