Fix copy/paste error in path check.

Function file is up above, this should be the variables file.

Test: ./build_symbol_db.py libcamera2ndk
Bug: None
Change-Id: I5ec8a7f3b10a46c984f3e8d3b74caf43ccc77910
diff --git a/ndk/build_symbol_db.py b/ndk/build_symbol_db.py
index e01ff18..00638f9 100755
--- a/ndk/build_symbol_db.py
+++ b/ndk/build_symbol_db.py
@@ -111,7 +111,7 @@
 
             vars_file_name = lib_name + '.so.variables.txt'
             vars_file = os.path.join(symbols_dir, vars_file_name)
-            if os.path.exists(funcs_file):
+            if os.path.exists(vars_file):
                 add_symbols(symbols, vars_file, version, arch, is_var='true')
     return symbols