Fix stack-use-after-scope in compiler test
Fix stack-use-after-scope in compiler test

The address sanitizer identified a stack-use-after-scope error in
a function used for tests. This commit fixes this error by ensuring
the path passed to the package_add_magic_path function is properly
copied.

kulibali/ponyc,cquinn/ponyc,kulibali/ponyc,dipinhora/ponyc,sgebbie/ponyc,dipinhora/ponyc,sgebbie/ponyc,jemc/ponyc,sgebbie/ponyc,ponylang/ponyc,ponylang/ponyc,sgebbie/ponyc,dipinhora/ponyc,jemc/ponyc,cquinn/ponyc,kulibali/ponyc,sgebbie/ponyc,jemc/ponyc,cquinn/ponyc,kulibali/ponyc,ponylang/ponyc,cquinn/ponyc