Make home_directory look in the password database in addition to $HOME.

This is something of an edge case, but when the $HOME environment
variable is not set, we can still look in the password database
to get the current user's home directory.

Added a test for this by getting the value of $HOME, then unsetting
it, then calling home_directory() and verifying that it succeeds
and that the value is the same as what we originally read from
the environment.

llvm-svn: 298513
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index 4883ade..afa5a5a 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -328,6 +328,26 @@
   }
 }
 
+#ifndef LLVM_ON_WIN32
+TEST(Support, HomeDirectoryWithNoEnv) {
+  std::string Original;
+  char const *path = ::getenv("HOME");
+  // Don't try to test if we don't have something to compare against.
+  if (!path)
+    return;
+  Original = path;
+  ::unsetenv("HOME");
+
+  SmallString<128> HomeDir;
+  auto status = path::home_directory(HomeDir);
+  EXPECT_TRUE(status);
+  EXPECT_EQ(Original, HomeDir);
+
+  // Now put the original environment variable back
+  ::setenv("HOME", Original.c_str(), 1);
+}
+#endif
+
 TEST(Support, UserCacheDirectory) {
   SmallString<13> CacheDir;
   SmallString<20> CacheDir2;