Support setting up the test-suite

Add a subcommand 'setup-test-suite' which sets up a sandbox that can be
used for running the test-suite.

Change-Id: If6426acd0e4e8ed54d310d1159a545f762affe74
diff --git a/helpers/llvm-test-suite b/helpers/llvm-test-suite
index 283e52f..0374749 100755
--- a/helpers/llvm-test-suite
+++ b/helpers/llvm-test-suite
@@ -19,9 +19,7 @@
 lit=$LLVM_BLD/bin/llvm-lit
 clang=$LLVM_BLD/bin/clang
 
-# TODO: There should be a llvm.py subcommand for setting up the sandbox
-safe_run virtualenv $sandbox
-safe_run $sandbox/bin/python $lnt/setup.py develop
+safe_run python3 $llvmtool setup-test-suite --sandbox $sandbox --lnt $lnt
 
 safe_run python3 $llvmtool run-test-suite --sandbox $sandbox \
   --test-suite $testsuite --use-lit $lit --cc $clang --cxx $clang++ "$@"