what are possible values for lit build_mode?

The page:

http://clang.llvm.org/hacking.html#testingNonWindows

contains:

You may also need to specify the build mode (Win32, etc) via --param=build_mode=(build mode).

However, other than Win32, no possible values for this parameter
are listed. Also, the lit page:

http://llvm.org/docs/CommandGuide/lit.html

does not mention build_mode.

I tried using --debug and added:

         print "litConfig.params=",litConfig.params

at the top of TestingConfig.finish(self, litConfig)

However, that didn't help ;( Here's the output:

make -f test.mk test1
python /home/evansl/dwnlds/llvm/git/llvm/utils/lit/lit.py -sv --param=build_mode=XXX --param=build_config=Release --param=clang_site_config=/home/evansl/dwnlds/llvm/git/build/release/object/tools/clang/test/lit.site.cfg /home/evansl/dwnlds/llvm/git/build/release/object/tools/clang/test/CXX/temp/temp.decls/temp.variadic/sizeofpack.cpp
lit.py: lit.cfg:201: note: using clang: '/home/evansl/dwnlds/llvm/git/build/release/object/Release+Asserts/bin/clang'
lit.py: lit.cfg:329: note: Did not find clang-interpreter in /home/evansl/dwnlds/llvm/git/build/release/object/Release+Asserts/bin:/home/evansl/dwnlds/llvm/git/build/release/object/Release+Asserts/bin
litConfig.params= {'build_config': 'Release', 'build_mode': 'XXX', 'clang_site_config': '/home/evansl/dwnlds/llvm/git/build/release/object/tools/clang/test/lit.site.cfg'}
litConfig.params= {'build_config': 'Release', 'build_mode': 'XXX', 'clang_site_config': '/home/evansl/dwnlds/llvm/git/build/release/object/tools/clang/test/lit.site.cfg'}
-- Testing: 1 tests, 1 threads --
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Testing Time: 0.02s
   Expected Passes : 1

Compilation finished at Thu Jul 17 09:45:17

As you can see, an obviously bogus value, XXX, was supplied for
build_mode, but no diagnostic was generated; hence, I'm puzzled
as to what use is made of this param value. Also, the output
indicates duplicate calls were made to TestingConfig.finish with
same value for litConfig. Is there any reason for that?

TIA.

-regards,
Larry

Forwarding to the develop list because that's
probably the better place to post this message.
Sorry for noise on user list.