Add "cwd" parameter to DAP launch request

This adds the "cwd" parameter to the DAP launch request.

This came up here:
    https://github.com/eclipse-cdt-cloud/cdt-gdb-adapter/issues/90
... and seemed like a good idea.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>

gdb/python/lib/gdb/dap/launch.py

@@ -23,12 +23,22 @@ from .server import request, capability
 from .startup import send_gdb, send_gdb_with_response, in_gdb_thread, exec_and_log
 
 
+# The program being launched, or None.  This should only be access
+# from the DAP thread.
 _program = None
 
 
 @in_gdb_thread
-def _set_args_env(args, env):
+def _launch_setup(program, cwd, args, env, stopAtBeginningOfMainSubprogram):
+    if cwd is not None:
+        exec_and_log("cd " + cwd)
+    if program is not None:
+        exec_and_log("file " + program)
     inf = gdb.selected_inferior()
+    if stopAtBeginningOfMainSubprogram:
+        main = inf.main_name
+        if main is not None:
+            exec_and_log("tbreak " + main)
     inf.arguments = args
     if env is not None:
         inf.clear_env()
@@ -36,14 +46,6 @@ def _set_args_env(args, env):
             inf.set_env(name, value)
 
 
-@in_gdb_thread
-def _break_at_main():
-    inf = gdb.selected_inferior()
-    main = inf.main_name
-    if main is not None:
-        exec_and_log("tbreak " + main)
-
-
 # Any parameters here are necessarily extensions -- DAP requires this
 # from implementations.  Any additions or changes here should be
 # documented in the gdb manual.
@@ -51,19 +53,17 @@ def _break_at_main():
 def launch(
     *,
     program: Optional[str] = None,
+    cwd: Optional[str] = None,
     args: Sequence[str] = (),
     env: Optional[Mapping[str, str]] = None,
     stopAtBeginningOfMainSubprogram: bool = False,
     **extra,
 ):
-    if program is not None:
-        global _program
-        _program = program
-        send_gdb("file " + _program)
-    if stopAtBeginningOfMainSubprogram:
-        send_gdb(_break_at_main)
-    if len(args) > 0 or env is not None:
-        send_gdb(lambda: _set_args_env(args, env))
+    global _program
+    _program = program
+    send_gdb(
+        lambda: _launch_setup(program, cwd, args, env, stopAtBeginningOfMainSubprogram)
+    )
 
 
 @request("attach")