[tools] Improve locs.py

- Detect errors during generation of compile_commands.json
  and building the target 'v8_generated_cc_files'.

- Change format of JSON output to have files as keys, which makes
  programmatic lookup by filename easier on the consumer side.

Change-Id: Ibc3d9cff64f82df7a3dbb76cb8d914b29460a48c
Notry: true
Reviewed-on: https://chromium-review.googlesource.com/c/1362041Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58263}

tools/locs.py

@@ -134,9 +134,17 @@ def GenerateCompileCommandsAndBuild(build_dir, compile_commands_file, out):
 
   ninja = "ninja -C {} -t compdb cxx cc > {}".format(
       build_dir, compile_commands_file)
-  subprocess.call(ninja, shell=True, stdout=out)
-  autoninja = "autoninja -C {}".format(build_dir)
-  subprocess.call(autoninja, shell=True, stdout=out)
+  if subprocess.call(ninja, shell=True, stdout=out) != 0:
+    print("Error: Cound not generate {} for {}.".format(
+      compile_commands_file, build_dir), file=sys.stderr)
+    exit(1)
+
+  autoninja = "autoninja -C {} v8_generated_cc_files".format(build_dir)
+  if subprocess.call(autoninja, shell=True, stdout=out) != 0:
+    print("Error: Building target 'v8_generated_cc_files'"
+      " failed for {}.".format(build_dir), file=sys.stderr)
+    exit(1)
+
   return compile_commands_file
 
 
@@ -219,7 +227,7 @@ def SetupReportGroups():
 class Results:
   def __init__(self):
     self.groups = SetupReportGroups()
-    self.units = []
+    self.units = {}
 
   def track(self, filename):
     is_tracked = False
@@ -230,7 +238,7 @@ class Results:
 
   def recordFile(self, filename, loc, expanded):
     unit = File(filename, loc, expanded)
-    self.units.append(unit)
+    self.units[filename] = unit
     for group in self.groups.values():
       group.account(unit)
 
@@ -242,7 +250,7 @@ class Results:
       print(self.groups[key].to_string(self.maxGroupWidth()), file=file)
 
   def printSorted(self, key, count, reverse, out):
-    for unit in sorted(self.units, key=key, reverse=reverse)[:count]:
+    for unit in sorted(list(self.units.values()), key=key, reverse=reverse)[:count]:
       print(unit.to_string(), file=out)
 
 
@@ -263,7 +271,7 @@ class StatusLine:
 
   def print(self, statusline, end="\r", file=sys.stdout):
     self.max_width = max(self.max_width, len(statusline))
-    print("{0:<{1}}".format(statusline, self.max_width), end=end, file=file)
+    print("{0:<{1}}".format(statusline, self.max_width), end=end, file=file, flush=True)
 
 
 class CommandSplitter: