[lldb] Do not accept invalid process save-core plugins (#142684)

Fixes #142581

Author: da-viper

lldb/source/Commands/CommandObjectProcess.cpp

@@ -1303,7 +1303,7 @@ class CommandObjectProcessSaveCore : public CommandObjectParsed {
         llvm_unreachable("Unimplemented option");
       }
 
-      return {};
+      return error;
     }
 
     void OptionParsingStarting(ExecutionContext *execution_context) override {

lldb/source/Symbol/SaveCoreOptions.cpp

@@ -24,7 +24,6 @@ Status SaveCoreOptions::SetPluginName(const char *name) {
   if (!PluginManager::IsRegisteredObjectFilePluginName(name)) {
     return Status::FromErrorStringWithFormat(
         "plugin name '%s' is not a valid ObjectFile plugin name", name);
-    return error;
   }
 
   m_plugin_name = name;

lldb/test/Shell/Commands/command-process-save-core-not-a-plugin.test

@@ -0,0 +1,19 @@
+# This checks that lldb returns an error if process save-core is called
+# with a plugin that does not exist.
+
+# RUN: %clang_host -g %S/Inputs/main.c -o %t
+# RUN: %lldb %t -s %s -o exit 2>&1 | FileCheck %s
+
+b main
+# CHECK-LABEL: b main
+# CHECK: Breakpoint 1: where = {{.*}}`main
+
+run
+# CHECK-LABEL: run
+# CHECK: Process {{.*}} stopped
+# CHECK: stop reason = breakpoint 1
+# CHECK:   frame #0: {{.*}}`main at main.c
+
+process save-core --plugin-name=notaplugin dump
+# CHECK-LABEL: process save-core --plugin-name=notaplugin dump
+# CHECK: error: plugin name 'notaplugin' is not a valid ObjectFile plugin name