[lldb] Require Clang 8 for gpubnames test

This test is using -gpubnames which is only available since Clang 8. The
original Clang 7 requirement was based on the availability of
-accel-tables=Dwarf (which the test initially used before being changed to
-gpubnames in commit 15a6df5 ).

Author: Teemperor

lldb/test/API/lang/c/forward/TestForwardDeclaration.py

@@ -58,7 +58,7 @@ def test(self):
     @no_debug_info_test
     @skipIfDarwin
     @skipIf(compiler=no_match("clang"))
-    @skipIf(compiler_version=["<", "7.0"])
+    @skipIf(compiler_version=["<", "8.0"])
     @expectedFailureAll(oslist=["windows"])
     def test_debug_names(self):
         """Test that we are able to find complete types when using DWARF v5