[lldb][test] Skip TestDataFormatterLibcxxStringSimulator.py for now

This fails on one of the compressed_pair layouts with:
```
Assertion failed: (M.Offset >= Tail && "Bitfield access unit is not clipped"), function checkBitfieldClipping, file CGRecordLayoutBuilder.cpp, line 960.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      <eof> parser at end of file
1.      <lldb wrapper prefix>:43:1: Generating code for declaration '$__lldb_expr'
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  liblldb.19.1.5.dylib     0x0000000143fc03fc llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  liblldb.19.1.5.dylib     0x0000000143fbe720 llvm::sys::RunSignalHandlers() + 112
2  liblldb.19.1.5.dylib     0x0000000143fc0a90 SignalHandler(int, __siginfo*, void*) + 360
3  libsystem_platform.dylib 0x00000001809c7624 _sigtramp + 56
4  libsystem_pthread.dylib  0x000000018098d88c pthread_kill + 296
5  libsystem_c.dylib        0x0000000180896c60 abort + 124
6  libsystem_c.dylib        0x0000000180895eec err + 0
7  liblldb.19.1.5.dylib     0x0000000144042708 (anonymous namespace)::CGRecordLowering::lower(bool) (.cold.70) + 0
8  liblldb.19.1.5.dylib     0x0000000141ab9f5c (anonymous namespace)::CGRecordLowering::lower(bool) + 10428
9  liblldb.19.1.5.dylib     0x0000000141ab6d80 clang::CodeGen::CodeGenTypes::ComputeRecordLayout(clang::RecordDecl const*, llvm::StructType*) + 240
10 liblldb.19.1.5.dylib     0x0000000141b7b980 clang::CodeGen::CodeGenTypes::ConvertRecordDeclType(clang::RecordDecl const*) + 352
11 liblldb.19.1.5.dylib     0x0000000141b7a6b4 clang::CodeGen::CodeGenTypes::ConvertTypeForMem(clang::QualType) + 172
12 liblldb.19.1.5.dylib     0x0000000141abb0e0 (anonymous namespace)::CGRecordLowering::getStorageType(clang::FieldDecl const*) const + 48
13 liblldb.19.1.5.dylib     0x0000000141ab7904 (anonymous namespace)::CGRecordLowering::lower(bool) + 612
```

But only on the Apple LLVM fork. Will need to investigate this separately

Author: Michael137

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py

@@ -13,6 +13,8 @@
 class LibcxxStringDataFormatterSimulatorTestCase(TestBase):
     NO_DEBUG_INFO_TESTCASE = True
 
+    @skipIfDarwin
+    @skipIfWindows
     def _run_test(self, defines):
         cxxflags_extras = " ".join(["-D%s" % d for d in defines])
         self.build(dictionary=dict(CXXFLAGS_EXTRAS=cxxflags_extras))