[Driver, Frontend] Use StringRef::contains (NFC)
diff --git a/clang/lib/Driver/ToolChains/FreeBSD.cpp b/clang/lib/Driver/ToolChains/FreeBSD.cpp
index 2753876..7ace08f 100644
--- a/clang/lib/Driver/ToolChains/FreeBSD.cpp
+++ b/clang/lib/Driver/ToolChains/FreeBSD.cpp
@@ -110,7 +110,7 @@
   for (const Arg *A : Args.filtered(options::OPT_ffile_prefix_map_EQ,
                                     options::OPT_fdebug_prefix_map_EQ)) {
     StringRef Map = A->getValue();
-    if (Map.find('=') == StringRef::npos)
+    if (!Map.contains('='))
       D.Diag(diag::err_drv_invalid_argument_to_option)
           << Map << A->getOption().getName();
     else {