[build] Fix RBE fallback on pkg, ddc and dyn bots.

Also fix --check-clean. `ninja target -t commands` reports the commands for the default target, fix to use `ninja -t commands target` instead.

Change-Id: Ice179290e75b083a96abadb7540ca960eafcc982
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/510440
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

tools/build.py

@@ -198,8 +198,8 @@ def RunOneBuildCommand(build_config, args, env):
     return 0
 
 
-def CheckCleanBuild(build_config, args, rbe, env):
-    explain_args = args + ['-n', '-d', 'explain']
+def CheckCleanBuild(build_config, args, rbe, targets, env):
+    explain_args = args[0:3] + ['-n', '-d', 'explain'] + targets
     print(' '.join(explain_args))
     process = subprocess.Popen(explain_args,
                                env=env,
@@ -218,7 +218,7 @@ def CheckCleanBuild(build_config, args, rbe, env):
         return 1
 
     if rbe:
-        list_args = args + ['-t', 'commands']
+        list_args = args[0:3] + ['-t', 'commands'] + targets
         print(' '.join(list_args))
         process = subprocess.Popen(list_args,
                                    env=env,
@@ -298,7 +298,11 @@ def Build(configs, env, options):
 
     if options.check_clean:
         for (build_config, args, rbe) in configs:
-            if CheckCleanBuild(build_config, args, rbe, env=env) != 0:
+            if CheckCleanBuild(build_config,
+                               args,
+                               rbe,
+                               options.build_targets,
+                               env=env) != 0:
                 return 1
 
     return 0