Spelling fix

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ae22479..3ac323e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -131,7 +131,7 @@
         set(target "${CMAKE_CURRENT_SOURCE_DIR}/${base_name}")
     endif()
 
-    # Linking to non-existant file is not desirable. At best you will have a
+    # Linking to non-existent file is not desirable. At best you will have a
     # dangling link, but when building in tree, this can create a symbolic link
     # to itself.
     if (EXISTS ${target} AND NOT EXISTS ${link})