Use sys.executable to launch another Python script

To make setup_apprtc.py work on Windows

Bug: webrtc:7602
Change-Id: I17c19c1cb8b2b71dafd90ae5f8be80e50c3397e9
No-Try: True
Reviewed-on: https://webrtc-review.googlesource.com/66660
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22715}
diff --git a/rtc_tools/testing/setup_apprtc.py b/rtc_tools/testing/setup_apprtc.py
index 697d503..3f5a166 100755
--- a/rtc_tools/testing/setup_apprtc.py
+++ b/rtc_tools/testing/setup_apprtc.py
@@ -30,14 +30,15 @@
   output_dir = os.path.abspath(argv[1])
 
   download_apprtc_path = os.path.join(SCRIPT_DIR, 'download_apprtc.py')
-  utils.RunSubprocessWithRetry([download_apprtc_path, output_dir])
+  utils.RunSubprocessWithRetry([sys.executable, download_apprtc_path,
+                                output_dir])
 
   build_apprtc_path = os.path.join(SCRIPT_DIR, 'build_apprtc.py')
   apprtc_src_dir = os.path.join(output_dir, 'apprtc', 'src')
   go_dir = os.path.join(output_dir, 'go')
   collider_dir = os.path.join(output_dir, 'collider')
-  utils.RunSubprocessWithRetry([build_apprtc_path, apprtc_src_dir,
-                                go_dir, collider_dir])
+  utils.RunSubprocessWithRetry([sys.executable, build_apprtc_path,
+                                apprtc_src_dir, go_dir, collider_dir])
 
 
 if __name__ == '__main__':