[libcxx] Allow use of ShTest in libc++ tests along with other changes.

Summary:
This patch allows the use of LIT's ShTest format in the libc++ test suite. ShTests have the suffix '.sh.cpp'. It also introduces a series of other changes. These changes are:

- More functionality including parsing test metadata has been moved into LIT.
- LibcxxTestFormat now supports multi-part suffixes.
- the `CXXCompiler` functionality has been used to shrink the size of LibcxxTestFormat. 
- The recursive loading of the site config has been turned into `libcxx.test.config.loadSiteConfig` so it can be used with libc++abi.
- Temporary files are now created in the build directory of libc++. This follows how it is down in ShTest.
- `not.py` was added as a utility executable that mirrors the functionality of LLVM's `not` executable. 
- The first ShTest test was added under test/libcxx/double_include.sh.cpp


Reviewers: jroelofs, danalbert

Reviewed By: danalbert

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D7073

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@226844 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/lit.cfg b/test/lit.cfg
index 385a433..f7fa614 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -15,37 +15,27 @@
 config.name = 'libc++'
 
 # suffixes: A list of file extensions to treat as test files.
-config.suffixes = ['.cpp']
+config.suffixes = ['.pass.cpp', '.fail.cpp', '.sh.cpp']
 
 # test_source_root: The root path where tests are located.
 config.test_source_root = os.path.dirname(__file__)
 
 # Infer the test_exec_root from the libcxx_object root.
-libcxx_obj_root = getattr(config, 'libcxx_obj_root', None)
-if libcxx_obj_root is not None:
-    config.test_exec_root = os.path.join(libcxx_obj_root, 'test')
+obj_root = getattr(config, 'libcxx_obj_root', None)
 
 # Check that the test exec root is known.
-if config.test_exec_root is None:
-    # Otherwise, we haven't loaded the site specific configuration (the user is
-    # probably trying to run on a test file directly, and either the site
-    # configuration hasn't been created by the build system, or we are in an
-    # out-of-tree build situation).
-    site_cfg = lit_config.params.get('libcxx_site_config',
-                                     os.environ.get('LIBCXX_SITE_CONFIG'))
-    if not site_cfg:
-        lit_config.warning('No site specific configuration file found!'
-                           ' Running the tests in the default configuration.')
-        # TODO: Set test_exec_root to a temporary directory where output files
-        # can be placed. This is needed for ShTest.
-    elif not os.path.isfile(site_cfg):
-        lit_config.fatal(
-            "Specified site configuration file does not exist: '%s'" %
-            site_cfg)
-    else:
-        lit_config.note('using site specific configuration at %s' % site_cfg)
-        lit_config.load_config(config, site_cfg)
-        raise SystemExit()
+if obj_root is None:
+    import libcxx.test.config
+    libcxx.test.config.loadSiteConfig(lit_config, config, 'libcxx_site_config',
+                                      'LIBCXX_SITE_CONFIG')
+    obj_root = getattr(config, 'libcxx_obj_root', None)
+    if obj_root is None:
+        import tempfile
+        obj_root = tempfile.mkdtemp(prefix='libcxx-testsuite-')
+        lit_config.warning('Creating temporary directory for object root: %s' %
+                           obj_root)
+
+config.test_exec_root = os.path.join(obj_root, 'test')
 
 cfg_variant = getattr(config, 'configuration_variant', 'libcxx')
 if cfg_variant: