Added code to ensure that no errors are returned due to concurent execution.
When running the compiler for the first time on a system, some directories are created in the tmp
directory, which may result in an error in case of multithreaded exexution. Similar errors may occur
when trying to create the core.a library or some library object files from concurent compiler instances.
The code added with this commit, makes sure that such errors are much less likely to occur.