[gdb/testsuite] Add boards/cc-with-index-cache.exp

We have a target board cc-with-gdb-index that uses the gdb-add-index script to
add a .gdb_index index to an exec.

There is however an alternative way of adding a .gdb_index: the index-cache.

Add a new target board cc-with-index-cache.

This is not superfluous for two reasons:
- there is functionality that gdb-add-index doesn't support, but the
  index-cache does: the index-cache can add an index to an exec with a
  .gnu_debugaltlink (note that when using the cc-with-gdb-index board this
  case is quietly ignored), and
- using the index-cache is excercised in only a few test-cases, and having
  this target board extends the test coverage to the entire test suite.  This
  is for instance relevant because the index-cache is written by a worker
  thread in the background, so we can check more thoroughly for data races
  (see PR symtab/30837).

Tested on x86_64-linux.

Shell script changes checked with shellcheck.

Approved-By: Tom Tromey <tom@tromey.com>

0 files changed, 0 insertions, 0 deletions