[lldb][test] Fix TestStdCXXDisassembly test (#112357)

The patch #98694 was not enough. This test is still failed on the
buildbot https://lab.llvm.org/staging/#/builders/195/builds/4438
Use `USE_LIBSTDCPP := 1` instead for non Darwin OS and skip the test if
libstdc++.so is missing.

Author: slydiman

lldb/test/API/lang/cpp/stl/Makefile

@@ -1,5 +1,9 @@
 CXX_SOURCES := main.cpp
 
-USE_SYSTEM_STDLIB := 1
+ifneq ($(OS),Darwin)
+    USE_LIBSTDCPP := 1
+else
+    USE_SYSTEM_STDLIB := 1
+endif
 
 include Makefile.rules

lldb/test/API/lang/cpp/stl/TestStdCXXDisassembly.py

@@ -43,7 +43,10 @@ def test_stdcxx_disasm(self):
         # At this point, lib_stdcxx is the full path to the stdc++ library and
         # module is the corresponding SBModule.
 
-        self.expect(lib_stdcxx, "Library StdC++ is located", exe=False, substrs=["lib"])
+        if "lib" not in lib_stdcxx:
+            self.skipTest(
+                "This test requires libstdc++.so or libc++.dylib in the target's module list."
+            )
 
         self.runCmd("image dump symtab '%s'" % lib_stdcxx)
         raw_output = self.res.GetOutput()