Add a missing backslash to a makefile

Closes #11874
Fix a typo in disable rpaths

Closes #5219
Update extract-tests.py to use same test directives as rustdoc.

Closes #11362.
auto merge of #11490 : wting/rust/wting_11362_update_extract_tests, r=alexcrichton

Refactored the file quite a bit, I can add unit tests if desired. There's a few changes from the previous version's behavior:

- destination directory will be created if it doesn't exist
- strings and file is written as unicode

I have a few questions, but will ask them in #11362.
auto merge of #11883 : alexcrichton/rust/fix-mk-install, r=pnkfelix

Closes #11874
auto merge of #11887 : alexcrichton/rust/rpath-for-real, r=thestinger

Closes #5219
Generate rlibs by default (instead of dylibs)

Closes #11253
auto merge of #11706 : alexcrichton/rust/issue-11253, r=huonw

Closes #11253
Document vector destructuring with wildcard '..'