[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

llvm-svn: 226844
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 74e82fa4f3c07aa388dfe41ebc300aeeaeb5a9cb
diff --git a/utils/not/not.py b/utils/not/not.py
new file mode 100644
index 0000000..96e4ea7
--- /dev/null
+++ b/utils/not/not.py
@@ -0,0 +1,35 @@
+"""not.py is a utility for inverting the return code of commands.
+It acts similar to llvm/utils/not.
+ex: python /path/to/not.py ' echo hello
+    echo $? // (prints 1)
+"""
+
+import distutils.spawn
+import subprocess
+import sys
+
+
+def main():
+    argv = list(sys.argv)
+    del argv[0]
+    if len(argv) > 0 and argv[0] == '--crash':
+        del argv[0]
+        expectCrash = True
+    else:
+        expectCrash = False
+    if len(argv) == 0:
+        return 1
+    prog = distutils.spawn.find_executable(argv[0])
+    if prog is None:
+        sys.stderr.write('Failed to find program %s' % argv[0])
+        return 1
+    rc = subprocess.call(argv)
+    if rc < 0:
+        return 0 if expectCrash else 1
+    if expectCrash:
+        return 1
+    return rc == 0
+
+
+if __name__ == '__main__':
+    exit(main())