Fix LD_LIBRARY_PATH for host tests after update.

_run never gets called any more, so the LD_LIBRARY_PATH wasn't being
set any more. The tests were still passing locally for me because the
tests were happily using the libc++.so from my system rather than the
one we build.

Wasn't obvious from the buildbot because the display for the test
results is absolutely terrible and they got lost in the noise of the
known failures.

Change-Id: Ib2df196ec6748718930e70887b7d0099884d792c

test/libcxx/android/test/format.py

@@ -17,10 +17,7 @@ class HostTestFormat(libcxx.test.format.LibcxxTestFormat):
         self.libcxx_obj_root = libcxx_obj_root
         self.use_verify_for_fail = False
         self.executor = TimeoutExecutor(timeout, LocalExecutor())
-        self.exec_env = {} if exec_env is None else exec_env
 
-    def _run(self, exec_path, _, in_dir=None):
-        cmd = [exec_path]
         # We need to use LD_LIBRARY_PATH because the build system's rpath is
         # relative, which won't work since we're running from /tmp. We can
         # either scan `cxx_under_test`/`link_template` to determine whether
@@ -32,9 +29,8 @@ class HostTestFormat(libcxx.test.format.LibcxxTestFormat):
             os.path.join(outdir, 'lib'),
             os.path.join(outdir, 'lib64'),
         ])
-        out, err, rc = lit.util.executeCommand(
-            cmd, cwd=in_dir, env={'LD_LIBRARY_PATH': libpath})
-        return self._make_report(cmd, out, err, rc)
+        default_env = {'LD_LIBRARY_PATH': libpath}
+        self.exec_env = default_env if exec_env is None else exec_env
 
 
 class TestFormat(HostTestFormat):