This reverts commit 951b107eedab1829f18049443f03339dbb0db165.

Buildbots were failing, there is a deadlock in /Users/gclayton/Documents/src/llvm/clean/llvm-project/lldb/test/Shell/SymbolFile/DWARF/DW_AT_range-DW_FORM_sec_offset.s when ELF files try to relocate things.

This reverts commit dd5505a8f2c75a903ec944b6e46aed2042610673.

I picked the wrong class for the test, should have been GDBRemoteTestBase.

Symbol table parsing has evolved over the years and many plug-ins contained duplicate code in the ObjectFile::GetSymtab() that used to be pure virtual. With this change, the "Symbtab *ObjectFile::GetSymtab()" is no longer virtual and will end up calling a new "void ObjectFile::ParseSymtab(Symtab &symtab)" pure virtual function to actually do the parsing. This helps centralize the code for parsing the symbol table and allows the ObjectFile base class to do all of the common work, like taking the necessary locks and creating the symbol table object itself. Plug-ins now just need to parse when they are asked to parse as the ParseSymtab function will only get called once.

Differential Revision: https://reviews.llvm.org/D113965

distutils is deprecated and will be removed, so we shouldn't be
using it.

We were using it to compute LLDB_PYTHON_RELATIVE_PATH.

Discussing a similar issue
[at python.org](https://bugs.python.org/issue41282), Filipe Laíns said:

    If you are relying on the value of distutils.sysconfig.get_python_lib()
    as you shown in your system, you probably don't want to. That
    directory (dist-packages) should be for Debian provided packages
    only, so moving to sysconfig.get_path() would be a good thing,
    as it has the correct value for user installed packages on your
    system.

So I propose using a relative path from `sys.prefix` to
`sysconfig.get_path("platlib")` instead.

On Mac and windows, this results in the same paths as we had before,
which are `lib/python3.9/site-packages` and `Lib\site-packages`,
respectively.

On ubuntu however, this will change the path from
`lib/python3/dist-packages` to `lib/python3.9/site-packages`.

This change seems to be correct, as Filipe said above, `dist-packages`
belongs to the distribution, not us.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D114106

see: https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/38387/console

```
Could not find a relative path to sys.executable under sys.prefix
tried: /usr/local/opt/python/bin/python3.7
tried: /usr/local/opt/python/bin/../Frameworks/Python.framework/Versions/3.7/bin/python3.7
sys.prefix: /usr/local/Cellar/python/3.7.1/Frameworks/Python.framework/Versions/3.7
```

It was unable to find LLDB_PYTHON_EXE_RELATIVE_PATH because it was not resolving
the real path of sys.prefix.

caused by: https://reviews.llvm.org/D113650

Testing the breakpoint itself rather than the lldb string.

Differential Revision: https://reviews.llvm.org/D111899

The reworking of the gdb client tests into the PlatformClientTestBase broke
the test for this.  I did the mutatis mutandis for the move, but the test
still fails.  Reverting till I have time to figure out why.

This reverts commit b715b79d54d5ca2d4e8c91089b8f6a9389d9dc48.

We don't actually need a local copy of the main executable to debug
a remote process.  So instead of treating "no local module" as an error,
see if the LaunchInfo has an executable it wants lldb to use, and if so
use it.  Then report whatever error the remote server returns.

Differential Revision: https://reviews.llvm.org/D113521