[libc++] Add from-scratch configuration files for the test suite

[ldionne]

Summary

This commit adds the first from-scratch configuration files for running
the libc++ test suite without using the old configuration:

• libcxx-trunk-shared.cfg.py: Runs the test suite against a trunk libc++ shared library.
• libcxx-trunk-static.cfg.py: Runs the test suite against a trunk libc++ static library.

[ldionne]

This is a WIP example of how to specify custom config files for running the libc++ test suite. The intent is that such config files can be checked into the repository, representing how different vendors run the test suite. For example, it would make sense to me to have a configuration for running the test suite with MSVC's library or libstdc++.

For those wondering why I'm doing that:

1. The more people we have running the test suite, the more people have an incentive to contribute to it and improve it, which means I get to do less of that and more of other stuff :-)
2. Having different Lit config files is going to remove a lot of complexity from the CMake build, where we have crazy settings for things like "build the shared library but link the tests against the static library". This shouldn't be part of CMake, it should just be a matter of selecting the right testing configuration.

[ldionne]

Remove the backdeployment config, which isn't quite ready yet.

libcxx/test/configs/libcxx-trunk-shared.cfg.in

+@AUTO_GEN_COMMENT@
+
+LIBCXX_ROOT = "@LIBCXX_SOURCE_DIR@"
+INSTALL_ROOT = "@CMAKE_BINARY_DIR@"
+COMPILER = "@CMAKE_CXX_COMPILER@"
+EXEC_ROOT = "@LIBCXX_BINARY_DIR@"
+
+import os
+import pipes
+import site
+import sys
+site.addsitedir(os.path.join(LIBCXX_ROOT, 'utils'))
+import libcxx.test.features
+import libcxx.test.format
+import libcxx.test.newconfig
+import libcxx.test.params
+
+# Configure basic properties of the test suite
+config.name = 'libcxx-trunk-shared'
+config.test_source_root = os.path.join(LIBCXX_ROOT, 'test')
+config.test_format = libcxx.test.format.CxxStandardLibraryTest()
+config.recursiveExpansionLimit = 10
+config.test_exec_root = EXEC_ROOT
+
+# Configure basic substitutions
+runPy = os.path.join(LIBCXX_ROOT, 'utils', 'run.py')
+config.substitutions.append(('%{cxx}', COMPILER))
+config.substitutions.append(('%{flags}', ''))
+config.substitutions.append(('%{compile_flags}', '-nostdinc++ -isystem {} -I {}'.format(os.path.join(INSTALL_ROOT, 'include', 'c++', 'v1'),
+                                                                                        os.path.join(LIBCXX_ROOT, 'test', 'support'))))
+config.substitutions.append(('%{link_flags}', '-nostdlib++ -L {0} -lc++ -Wl,-rpath,{0}'.format(os.path.join(INSTALL_ROOT, 'lib'))))
+config.substitutions.append(('%{exec}', '{} {} --execdir %T -- '.format(pipes.quote(sys.executable), pipes.quote(runPy))))
+
+# Add parameters and features to the config
+libcxx.test.newconfig.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)

libcxx/test/configs/libcxx-trunk-static.cfg.in

+@AUTO_GEN_COMMENT@
+
+LIBCXX_ROOT = "@LIBCXX_SOURCE_DIR@"
+INSTALL_ROOT = "@CMAKE_BINARY_DIR@"
+COMPILER = "@CMAKE_CXX_COMPILER@"
+EXEC_ROOT = "@LIBCXX_BINARY_DIR@"
+
+import os
+import pipes
+import site
+import sys
+site.addsitedir(os.path.join(LIBCXX_ROOT, 'utils'))
+import libcxx.test.features
+import libcxx.test.format
+import libcxx.test.newconfig
+import libcxx.test.params
+
+# Configure basic properties of the test suite
+config.name = 'libcxx-trunk-static'
+config.test_source_root = os.path.join(LIBCXX_ROOT, 'test')
+config.test_format = libcxx.test.format.CxxStandardLibraryTest()
+config.recursiveExpansionLimit = 10
+config.test_exec_root = EXEC_ROOT
+
+# Configure basic substitutions
+runPy = os.path.join(LIBCXX_ROOT, 'utils', 'run.py')
+config.substitutions.append(('%{cxx}', COMPILER))
+config.substitutions.append(('%{flags}', ''))
+config.substitutions.append(('%{compile_flags}', '-nostdinc++ -isystem {} -I {}'.format(os.path.join(INSTALL_ROOT, 'include', 'c++', 'v1'),
+                                                                                        os.path.join(LIBCXX_ROOT, 'test', 'support'))))
+config.substitutions.append(('%{link_flags}', '-nostdlib++ {} {}'.format(os.path.join(INSTALL_ROOT, 'lib', 'libc++.a'),
+                                                                         os.path.join(INSTALL_ROOT, 'lib', 'libc++abi.a'))))
+config.substitutions.append(('%{exec}', '{} {} --execdir %T -- '.format(pipes.quote(sys.executable), pipes.quote(runPy))))
+
+# Add parameters and features to the config
+libcxx.test.newconfig.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)