[lldb] Fix TestErrorMessages test on standalone builds by adding lldb-server substitution

[teemperor]

Summary

It seems that TestErrorMessages.test is failing on the standalone + Xcode builds as lldb-server executable
can't be found by lit's default PATH search. I assume invoking lldb-server via a lit substitution
gets this working again as everything else is working, so that's what this patch is doing.

I had to add the lldb-server substitution as the test seems lldb-server specific and we don't want it to default
to debugserver on Darwin.

Using a substitution also seems in general like a good idea so that the commands lit is printing on failure
are using the full path to lldb-server and can be re-run in a terminal.

[labath]

lldb/test/Shell/helper/toolchain.py

65–68

I guess we don't need this then, as one can just write %lldb-server platform. It also seems to be unused.

[teemperor]

lldb/test/Shell/helper/toolchain.py

65–68

It seems the test that was using this substitution was accidentally deleted in the lldb-mi removal, so I reinstated that test.

[JDevlieghere]

Please add a _disallow to avoid accidental use of lldb-server without the %.

[teemperor]

Added the disallow in rG7211604220ae

lldb/test/Shell/helper/toolchain.py

primary_tools = [
         ToolSubst('%lldb',
                   command=FindTool('lldb'),
                   extra_args=['--no-lldbinit', '-S', lldb_init],
                   unresolved='fatal'),
         ToolSubst('%lldb-init',
                   command=FindTool('lldb'),
                   extra_args=['-S', lldb_init],
                   unresolved='fatal'),
+        ToolSubst('%lldb-server',
+                  command=FindTool("lldb-server"),
+                  extra_args=[],
+                  unresolved='ignore'),
         ToolSubst('%debugserver',
                   command=FindTool(dsname),
                   extra_args=dsargs,
                   unresolved='ignore'),
         ToolSubst('%platformserver',
                   command=FindTool('lldb-server'),
                   extra_args=['platform'],
                   unresolved='ignore'),
         'lldb-test',
         'lldb-instr',
         'lldb-vscode',
         ToolSubst('%build',
                   command="'" + sys.executable + "'",
                   extra_args=build_script_args)
         ]
 

lldb/test/Shell/lldb-server/TestErrorMessages.test

-RUN: lldb-server gdbserver --fd 2>&1 | FileCheck --check-prefixes=FD1,ALL %s
+RUN: %lldb-server gdbserver --fd 2>&1 | FileCheck --check-prefixes=FD1,ALL %s
 FD1: error: --fd: missing argument
 
-RUN: lldb-server gdbserver --fd three 2>&1 | FileCheck --check-prefixes=FD2,ALL %s
+RUN: %lldb-server gdbserver --fd three 2>&1 | FileCheck --check-prefixes=FD2,ALL %s
 FD2: error: invalid '--fd' argument
 
-RUN: lldb-server gdbserver --bogus 2>&1 | FileCheck --check-prefixes=BOGUS,ALL %s
+RUN: %lldb-server gdbserver --bogus 2>&1 | FileCheck --check-prefixes=BOGUS,ALL %s
 BOGUS: error: unknown argument '--bogus'
 
-RUN: lldb-server gdbserver 2>&1 | FileCheck --check-prefixes=CONN,ALL %s
+RUN: %lldb-server gdbserver 2>&1 | FileCheck --check-prefixes=CONN,ALL %s
 CONN: error: no connection arguments
 
 ALL: Use '{{.*}} g[dbserver] --help' for a complete list of options.