Fix SyntaxWarning in build/run_tests.py

Use r-strings for all regular expressions.

Fixes these warnings experienced with Python 3.12
(python/cpython#98401,
python/cpython#99011,
https://docs.python.org/3/whatsnew/3.12.html#other-language-changes
point 2):

run_tests.py:200: SyntaxWarning: invalid escape sequence '\d'
  FINAL_LINE_RE = re.compile('status=(\d+)$')
run_tests.py:441: SyntaxWarning: invalid escape sequence '\*'
  re.match('^\* daemon .+ \*$', line) or line == ''):

Change-Id: I71ddfb1a2ca62654378ae67a99e9aeb4ce7b7394
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/6254063
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>

build/run_tests.py

@@ -79,7 +79,7 @@ def _BinaryDirTargetOS(binary_dir):
                                  text=True)
         value = popen.communicate()[0]
         if popen.returncode == 0:
-            match = re.match('target_os = "(.*)"$', value)
+            match = re.match(r'target_os = "(.*)"$', value)
             if match:
                 return match.group(1)
 
@@ -89,7 +89,7 @@ def _BinaryDirTargetOS(binary_dir):
     if os.path.exists(build_ninja_path):
         with open(build_ninja_path) as build_ninja_file:
             build_ninja_content = build_ninja_file.read()
-            match = re.search('-linux-android(eabi)?-ar$', build_ninja_content,
+            match = re.search(r'-linux-android(eabi)?-ar$', build_ninja_content,
                               re.MULTILINE)
             if match:
                 return 'android'
@@ -197,7 +197,7 @@ def _adb_shell(command_args, env={}):
                                  stdout=subprocess.PIPE,
                                  text=True)
 
-        FINAL_LINE_RE = re.compile('status=(\d+)$')
+        FINAL_LINE_RE = re.compile(r'status=(\d+)$')
         final_line = None
         while True:
             # Use readline so that the test output appears “live” when running.
@@ -438,7 +438,7 @@ def main(args):
             for line in adb_devices.splitlines():
                 line = line
                 if (line == 'List of devices attached' or
-                        re.match('^\* daemon .+ \*$', line) or line == ''):
+                        re.match(r'^\* daemon .+ \*$', line) or line == ''):
                     continue
                 (device, ignore) = line.split('\t')
                 devices.append(device)