[Docs] TestingGuide.rst: Fix incorrect description

[DamonFool]

Summary

This patch fixes two incorrect descriptions in TestingGuide.rst.

1. test/lit.site.cfg --> test/lit.site.cfg.py After https://reviews.llvm.org/D37838 , the test/lit.site.cfg had been added a .py extension. So it should be test/lit.site.cfg.py.

2. $(LLVM_OBJ_ROOT)/$(BuildMode)/bin --> $(LLVM_OBJ_ROOT)/bin The current build system doesn't create a $(BuildMode) directory any more. So it should be removed.

[mehdi_amini]

Do you have commit access or do you need someone to land this for you?

[MaskRay]

Thank you for refreshing the doc!

(You may remove greetings "Hi all," and "Thanks. Best regards, Jie" from the summary/commit message.)

[DamonFool]

Thanks @mehdi_amini and @MaskRay for your review.

[DamonFool]

In D140780#4020331, @mehdi_amini wrote:

Do you have commit access or do you need someone to land this for you?

I'm new in LLVM, so I don't have commit access.
I need your help to land this patch.

Please use “Jie Fu [e-mail]” to commit the change.
Thanks.

[DamonFool]

In D140780#4020388, @MaskRay wrote:

Thank you for refreshing the doc!

(You may remove greetings "Hi all," and "Thanks. Best regards, Jie" from the summary/commit message.)

Got it and done.
Thanks.

[MaskRay]

llvm/docs/TestingGuide.rst

238

i'll move ) after the quote.

[DamonFool]

Thanks @MaskRay for your help.

llvm/docs/TestingGuide.rst

 The directory is broken into several sub-directories, each focused on a
 particular area of LLVM.
 
 Writing new regression tests
 ----------------------------
 
 The regression test structure is very simple, but does require some
 information to be set. This information is gathered via ``cmake``
-and is written to a file, ``test/lit.site.cfg`` in the build directory.
+and is written to a file, ``test/lit.site.cfg.py`` in the build directory.
 The ``llvm/test`` Makefile does this work for you.
 
 In order for the regression tests to work, each directory of tests must
 have a ``lit.local.cfg`` file. :program:`lit` looks for this file to determine
 how to run the tests. This file is just Python code and thus is very
 flexible, but we've standardized it for the LLVM regression tests. If
 you're adding a directory of tests, just copy ``lit.local.cfg`` from
 another directory to get running. The standard ``lit.local.cfg`` simply

 shell's syntax for pipelines including I/O redirection and variable
 substitution. However, even though these lines may *look* like a shell
 script, they are not. RUN lines are interpreted by :program:`lit`.
 Consequently, the syntax differs from shell in a few ways. You can specify
 as many RUN lines as needed.
 
 :program:`lit` performs substitution on each RUN line to replace LLVM tool names
 with the full paths to the executable built for each tool (in
-``$(LLVM_OBJ_ROOT)/$(BuildMode)/bin)``. This ensures that :program:`lit` does
+``$(LLVM_OBJ_ROOT)/bin)``. This ensures that :program:`lit` does
 not invoke any stray LLVM tools in the user's path during testing.
 
 Each RUN line is executed on its own, distinct from other lines unless
 its last character is ``\``. This continuation character causes the RUN
 line to be concatenated with the next one. In this way you can build up
 long pipelines of commands without making huge line lengths. The lines
 ending in ``\`` are concatenated until a RUN line that doesn't end in
 ``\`` is found. This concatenated set of RUN lines then constitutes one