Fix rust_unittests with asan, part 2

I fixed it in an earlier patchset of the previous commit and then accidentally rolled the fix back.

Bug: 528225104
Change-Id: Id9fc94fda2ed8c410f8a71db3f6e253c6a6a6964
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/25120
Commit-Queue: Matt Stark <msta@google.com>
Reviewed-by: Takuto Ikuta <tikuta@google.com>

src/gn/ffi/test_with_scope.h

diff --git a/src/gn/ffi/test_with_scope.h b/src/gn/ffi/test_with_scope.h
index eb16e90..db67e82 100644
--- a/src/gn/ffi/test_with_scope.h
+++ b/src/gn/ffi/test_with_scope.h
@@ -5,18 +5,30 @@
 #ifndef TOOLS_GN_FFI_TEST_WITH_SCOPE_H_
 #define TOOLS_GN_FFI_TEST_WITH_SCOPE_H_
 
+#include <cstdlib>
 #include <memory>
+#include <mutex>
 
 #include "base/command_line.h"
 #include "gn/scheduler.h"
 #include "gn/test_with_scope.h"
 
 inline std::unique_ptr<TestWithScope> NewTestWithScope() {
-  if (!base::CommandLine::InitializedForCurrentProcess()) {
-    int argc = 1;
-    const char* argv[] = {"gn_rust_tests", nullptr};
-    base::CommandLine::Init(argc, argv);
-  }
+  static std::once_flag init_flag;
+  std::call_once(init_flag, []() {
+    if (!base::CommandLine::InitializedForCurrentProcess()) {
+      int argc = 1;
+      const char* argv[] = {"gn_rust_tests", nullptr};
+      base::CommandLine::Init(argc, argv);
+      // Since this is used in rust, rather than trying to attach the lifetime
+      // to anything, we just attach it to the process itself.
+      std::atexit([]() {
+        if (base::CommandLine::InitializedForCurrentProcess()) {
+          base::CommandLine::Reset();
+        }
+      });
+    }
+  });
   // Initialize a single Scheduler instance that lives for the lifetime of the
   // test process. This ensures g_scheduler is always set and never cleared
   // between tests.