fix broken separator line of lsp-headerline (emacs-lsp#3545)

* fix broken separator line of lsp-headerline

* redefine all-the-icons' vars to avoid compilation errors

Author: taquangtrung

lsp-headerline.el

@@ -143,15 +143,21 @@ is an hints in symbols range."
   "Holds the current breadcrumb path-up-to-project segments for
 caching purposes.")
 
+;; Redefine local vars of `all-the-icons' to avoid bytecode compilation errors.
+(defvar all-the-icons-default-adjust)
+(defvar all-the-icons-scale-factor)
+
 (defun lsp-headerline--arrow-icon ()
   "Build the arrow icon for headerline breadcrumb."
   (or
    lsp-headerline-arrow
-   (setq lsp-headerline-arrow (lsp-icons-all-the-icons-material-icon
-                               "chevron_right"
-                               'lsp-headerline-breadcrumb-separator-face
-                               ">"
-                               'headerline-breadcrumb))))
+   (setq lsp-headerline-arrow (let ((all-the-icons-scale-factor 1.0)
+                                    (all-the-icons-default-adjust 0))
+                                (lsp-icons-all-the-icons-material-icon
+                                 "chevron_right"
+                                 'lsp-headerline-breadcrumb-separator-face
+                                 ">"
+                                 'headerline-breadcrumb)))))
 
 (lsp-defun lsp-headerline--symbol-icon ((&DocumentSymbol :kind))
   "Build the SYMBOL icon for headerline breadcrumb."