Auto merge of #4818 - alexcrichton:rename-link-paths, r=matklad

Auto merge of #4818 - alexcrichton:rename-link-paths, r=matklad

Fix renaming a project using build scripts

This commit fixes an issue in Cargo where if a project's folder was
renamed but it also contained a build script the project could break.
Cargo would continue to use the previous `rustc-link-search` arguments
to configure env vars like `LD_LIBRARY_PATH` but the literal values from
the previous compilation would be stale as the directories would no
longer be there.

To fix this when parsing the build script output we now retain a log of
the previous output directory of a build script invocation as well as
the current output, tweaking paths as appropriate if they were contained
in the output folder.

Closes #4053