Since September, the toolchain has not been generating reliable DWARF
information for static variables when LTO is on. This has affected
projects in the embedded space where the use of LTO is typical. In our
case, it has kept us from bumping past the 2021-09-22 nightly toolchain
lest our debugger break. This has been a pretty dramatic regression for
people using debuggers and static variables. See rust-lang#90357 for more info
and a repro case.

This commit is a mechanical revert of
d5de680 from PR rust-lang#89041, which caused
the issue. (Note on that PR that the commit's author has requested it be
reverted.)

I have locally verified that this fixes rust-lang#90357 by restoring the
functionality of both the repro case I posted on that bug, and debugger
behavior on real programs. There do not appear to be test cases for this
in the toolchain; if I've missed them, point me at 'em and I'll update
them.

- Re-enabled basic-types-globals which has been disabled since 2018
- Updated its now-rotted assertions about GDB's output to pass
- Rewrote header comment describing some previous state of GDB behavior
  that didn't match either the checked-in assertions _or_ the current
  behavior, and so I assume has just been wrong for some time.
- Copy-pasta'd the test into a version that uses LTO to check for
  regression on rust-lang#90357, because I don't see a way to matrix the same
  test into several build configurations.