Gender-neutralize a comment.

llvm-svn: 231891
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 3c6827a..e378ee8 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -8065,8 +8065,8 @@
   if (!llvm::sys::Process::GetEnv("LIB")) {
     // If the VC environment hasn't been configured (perhaps because the user
     // did not run vcvarsall), try to build a consistent link environment.  If
-    // the environment variable is set however, assume the user knows what he's
-    // doing.
+    // the environment variable is set however, assume the user knows what
+    // they're doing.
     std::string VisualStudioDir;
     const auto &MSVC = static_cast<const toolchains::MSVCToolChain &>(TC);
     if (MSVC.getVisualStudioInstallDir(VisualStudioDir)) {