Enable libc++ in the build for libcxx initializerlist pretty printers

Differential Revision: https://reviews.llvm.org/D112163

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/initializerlist/Makefile

@@ -1,4 +1,6 @@
 CXX_SOURCES := main.cpp
 CXXFLAGS_EXTRAS := -std=c++11
 
+USE_LIBCPP := 1
+
 include Makefile.rules

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/initializerlist/TestInitializerList.py

@@ -14,11 +14,7 @@ class InitializerListTestCase(TestBase):
 
     mydir = TestBase.compute_mydir(__file__)
 
-    @skipIfWindows  # libc++ not ported to Windows yet
-    @skipIf(compiler="gcc")
-    @expectedFailureAll(
-        oslist=["linux"],
-        bugnumber="fails on clang 3.5 and tot")
+    @add_test_categories(["libc++"])
     def test(self):
         """Test that that file and class static variables display correctly."""
         self.build()