Enable a test in TestSTL for GCC.

[sivachandra]

Summary

Remove @skipIfGcc from a test in TestSTL as that test passes with GCC
now. Also, mark one of the dsym tests with @skipUnlessDarwin in TestSTL.

lldb/trunk/test/lang/cpp/stl/TestSTL.py

class STLTestCase(TestBase):
     @dwarf_test
     def test_with_dwarf(self):
         """Test some expressions involving STL data types."""
         self.buildDwarf()
         self.step_stl_exprs()
 
     @python_api_test
     @dsym_test
+    @skipUnlessDarwin
     def test_SBType_template_aspects_with_dsym(self):
         """Test APIs for getting template arguments from an SBType."""
         self.buildDsym()
         self.sbtype_template_apis()
 
-    @skipIfGcc # llvm.org/pr15036: crashes during DWARF parsing when built with GCC
     @expectedFailureIcc # icc 13.1 and 14-beta do not emit DW_TAG_template_type_parameter
     @python_api_test
     @dwarf_test
     def test_SBType_template_aspects_with_dwarf(self):
         """Test APIs for getting template arguments from an SBType."""
         self.buildDwarf()
         self.sbtype_template_apis()