[lldb] skip unnamed symbol test on windows (#141212)

https://lab.llvm.org/buildbot/#/builders/141/builds/8927/steps/6/logs/stdio

Author: eronnen

lldb/test/API/python_api/unnamed_symbol_lookup/TestUnnamedSymbolLookup.py

@@ -8,7 +8,8 @@
 from lldbsuite.test.lldbtest import *
 from lldbsuite.test import lldbutil
 
-
+# --keep-symbol causes error on Windows: llvm-strip.exe: error: option is not supported for COFF
+@skipIfWindows
 class TestUnnamedSymbolLookup(TestBase):
     def test_unnamed_symbol_lookup(self):
         """Test looking up unnamed symbol synthetic name"""