Speed up Soong integration tests.

This is done by running a build before the first test case, tarring up
$TOP (including out/) then untarring it for every test case instead of
rebuilding soong_build each time.

The speedup is approximately 2x.

Also add some cute ANSI escape sequences and delineation of individual
test cases.

Test: The aforementioned integration tests.
Change-Id: I6a98660cfe6a40bcaa978e8d7544cdffad86a7fa
diff --git a/tests/mixed_mode_test.sh b/tests/mixed_mode_test.sh
index 54f0689..7dbafea 100755
--- a/tests/mixed_mode_test.sh
+++ b/tests/mixed_mode_test.sh
@@ -8,7 +8,7 @@
 
 source "$(dirname "$0")/lib.sh"
 
-function setup_bazel() {
+function create_mock_bazel() {
   copy_directory build/bazel
 
   symlink_directory prebuilts/bazel
@@ -20,7 +20,7 @@
 
 function test_bazel_smoke {
   setup
-  setup_bazel
+  create_mock_bazel
 
   tools/bazel info
 }