Add a new 'hint' argument for LLVMBuildFactory factory class. (#223)

This parameter is used to apply suffixes to the step names when factory
is used as a nested factory for another one. The suffix will be added to
the step name separated by dash symbol.

As example for 'stageX' hint the following step names will be generated
for the factory's steps:
    cmake-cofigure => cmake-configure-stageX
    build => build-<target>-stageX

Author: vvereschaka

zorg/buildbot/process/factory.py

@@ -23,12 +23,24 @@ class LLVMBuildFactory(BuildFactory):
 
     enable_runtimes is a list of enabled runtimes. If None,
     it gets discovered based on the depends_on_projects list.
+    
+    hint : string, optional
+        Use this hint to apply suffixes to the step names when factory is used as a nested factory for another one.
+        The suffix will be added to the step name separated by dash symbol.
+        
+        As example, passing of 'stageX' with 'hint' will force generating of the following step names:
+            cmake-cofigure => cmake-configure-stageX
+            build => build-stageX
+            install => install-stageX
+            & etc.
     """
 
-    def __init__(self, steps=None, depends_on_projects=None, **kwargs):
+    def __init__(self, steps=None, depends_on_projects=None, hint=None, **kwargs):
         # Cannot use "super" here as BuildFactory is an old style class.
         BuildFactory.__init__(self, steps)
 
+        self.hint = hint
+        
         # Handle the dependencies.
         if depends_on_projects is None:
             # llvm project is always included.
@@ -141,12 +153,16 @@ def pathRelativeTo(path, basePath):
 
             return rel_path
 
-
+    def makeStepName(self, name):
+        assert name, "The step name agrument cannot be empty."
+        return f"{name}-{self.hint}" if self.hint else name
+        
     def addGetSourcecodeSteps(self, **kwargs):
         # Checkout the monorepo.
         # Documentation: http://docs.buildbot.net/current/manual/configuration/buildsteps.html#git
         self.addStep(steps.Git(
-                name='Checkout the source code',
+                name=self.makeStepName('checkout'),
+                description='Checkout the source code',
                 repourl=self.repourl_prefix + "llvm-project.git",
                 progress=True,
                 workdir=util.Interpolate(self.monorepo_dir),
@@ -176,7 +192,7 @@ def addGetSourcecodeForProject(self, project, name=None, src_dir=None, **kwargs)
         kwargs.pop('workdir', None)
 
         self.addStep(steps.Git(
-                name=name,
+                name=self.makeStepName(name),
                 repourl=_repourl,
                 progress=True,
                 workdir=util.Interpolate(src_dir),