Support leak sanitizer in libcxx.

[saugustine]

Summary

Support leak sanitizer in libcxx.

Simple addition for leak checking when running the libcxx testsuite.

libcxx/test/libcxx/gdb/gdb_pretty_printer_test.py

def invoke(self, arg, from_tty):
         try:
             # Stack frame is:
             # 0. StopForDebugger
             # 1. ComparePrettyPrintToChars or ComparePrettyPrintToRegex
             # 2. TestCase
             compare_frame = gdb.newest_frame().older()
             testcase_frame = compare_frame.older()
             test_loc = testcase_frame.find_sal()
-
-            expectation_val = compare_frame.read_var("expectation")
-            check_literal = expectation_val.string(encoding="utf-8")
-
-            # Heuristic to determine if libc++ itself has debug
-            # info. If it doesn't, then anything normally homed there
-            # won't be found, and the printer will error. We don't
-            # want to fail the test in this case--the printer itself
-            # is probably fine, or at least we can't tell.
-            if check_literal.startswith("std::shared_ptr"):
-                shared_ptr = compare_frame.read_var("value")
-                if not "__shared_owners_" in shared_ptr.type.fields():
-                    print("IGNORED (no debug info in libc++): " +
-                          test_loc.symtab.filename + ":" +
-                          str(test_loc.line))
-                    return
-
             # Use interactive commands in the correct context to get the pretty
             # printed version
 
             value_str = self._get_value_string(compare_frame, testcase_frame)
 
             # Ignore the convenience variable name and newline
             value = value_str[value_str.find("= ") + 2:-1]
             gdb.newest_frame().select()

libcxx/utils/libcxx/test/config.py

def configure_sanitizer(self):
                 add_ubsan()
                 self.cxx.compile_flags += ['-O2']
             elif san == 'Thread':
                 self.cxx.flags += ['-fsanitize=thread']
                 self.config.available_features.add('tsan')
                 self.config.available_features.add('sanitizer-new-delete')
             elif san == 'DataFlow':
                 self.cxx.flags += ['-fsanitize=dataflow']
+            elif san == 'Leaks':
+                self.cxx.link_flags += ['-fsanitize=leaks']
             else:
                 self.lit_config.fatal('unsupported value for '
                                       'use_sanitizer: {0}'.format(san))
             san_lib = self.get_lit_conf('sanitizer_library')
             if san_lib:
                 self.cxx.link_flags += [
                     san_lib, '-Wl,-rpath,%s' % os.path.dirname(san_lib)]