[tools] Fix merging sancov files from multiple test attempts

tools/sanitizers/sancov_merger.py

 #!/usr/bin/env python
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Script for merging sancov files in parallel.
 
 When merging test runner output, the sancov files are expected
 to be located in one directory with the file-name pattern:
-<executable name>.test.<id>.sancov
+<executable name>.test.<id>.<attempt>.sancov
 
 For each executable, this script writes a new file:
 <executable name>.result.sancov
 
 When --swarming-output-dir is specified, this script will merge the result
 files found there into the coverage folder.
 
 The sancov tool is expected to be in the llvm compiler-rt third-party
 directory. It's not checked out by default and must be added as a custom deps:
 'v8/third_party/llvm/projects/compiler-rt':
@@ skipping 20 matching lines @@
 # The sancov tool location.
 SANCOV_TOOL = os.path.join(
     BASE_DIR, 'third_party', 'llvm', 'projects', 'compiler-rt',
     'lib', 'sanitizer_common', 'scripts', 'sancov.py')
 
 # Number of cpus.
 CPUS = cpu_count()
 
 # Regexp to find sancov file as output by the v8 test runner. Also grabs the
 # executable name in group 1.
-SANCOV_FILE_RE = re.compile(r'^(.*)\.test\.\d+\.sancov$')
+SANCOV_FILE_RE = re.compile(r'^(.*)\.test\.\d+\.\d+\.sancov$')
 
 # Regexp to find sancov result files as returned from swarming.
 SANCOV_RESULTS_FILE_RE = re.compile(r'^.*\.result\.sancov$')
 
 
 def merge(args):
   """Merge several sancov files into one.
 
   Called trough multiprocessing pool. The args are expected to unpack to:
     keep: Option if source and intermediate sancov files should be kept.
@@ skipping 158 matching lines @@
             os.path.isdir(options.swarming_output_dir))
     merge_swarming_output(options)
   else:
     merge_test_runner_output(options)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())