add likely/unlikely macro for unsupport c++20 compiler. (pytorch#124997)

# Issue:
Intel validation team found some low version gcc which not support c++20 will occur below issue:
```cmd
[2024-04-13T08:03:25.142Z] g++ /tmp/torchinductor_root/vd/cvdytwwwlhi63ofh3pwzqfpjga4w4xe7bjfdoavpblbo5khzf3b2.cpp -shared -fPIC -Wall -std=c++17 -Wno-unused-variable -Wno-unknown-pragmas -D_GLIBCXX_USE_CXX11_ABI=0 -I/root/anaconda3/envs/pytorch/lib/python3.8/site-packages/torch/include -I/root/anaconda3/envs/pytorch/lib/python3.8/site-packages/torch/include/torch/csrc/api/include -I/root/anaconda3/envs/pytorch/lib/python3.8/site-packages/torch/include/TH -I/root/anaconda3/envs/pytorch/lib/python3.8/site-packages/torch/include/THC -I/root/anaconda3/envs/pytorch/include/python3.8 -L/root/anaconda3/envs/pytorch/lib/python3.8/site-packages/torch/lib -L/root/anaconda3/envs/pytorch/lib -L/root/anaconda3/envs/pytorch/lib/python3.8/site-packages/torch/lib -ltorch -ltorch_cpu -lgomp -ltorch_python -lc10 -mavx2 -mfma -DCPU_CAPABILITY_AVX2 -O3 -DNDEBUG -ffast-math -fno-finite-math-only -fno-unsafe-math-optimizations -ffp-contract=off -march=native -fopenmp -D C10_USING_CUSTOM_GENERATED_MACROS -o /tmp/torchinductor_root/vd/cvdytwwwlhi63ofh3pwzqfpjga4w4xe7bjfdoavpblbo5khzf3b2.so
[2024-04-13T08:03:25.142Z]
[2024-04-13T08:03:25.142Z] Output:
[2024-04-13T08:03:25.142Z] /tmp/torchinductor_root/vd/cvdytwwwlhi63ofh3pwzqfpjga4w4xe7bjfdoavpblbo5khzf3b2.cpp: In function ‘T parse_arg(PyObject*, size_t) [with T = long int; PyObject = _object; size_t = long unsigned int]’:
[2024-04-13T08:03:25.142Z] /tmp/torchinductor_root/vd/cvdytwwwlhi63ofh3pwzqfpjga4w4xe7bjfdoavpblbo5khzf3b2.cpp:117:10: error: expected identifier before ‘[’ token
[2024-04-13T08:03:25.142Z] [[unlikely]] throw std::runtime_error("expected int arg");
[2024-04-13T08:03:25.142Z] ^
```

The season is `unlikely` need c++20 attribute, ref: https://en.cppreference.com/w/cpp/language/attributes/likely

# Solution:
Add MACRO to enable non-c++20 attribute GNU compiler.

Pull Request resolved: pytorch#124997
Approved by: https://github.com/jgong5, https://github.com/jansel

torch/_inductor/codecache.py

@@ -2210,6 +2210,15 @@ class CppPythonBindingsCodeCache(CppCodeCache):
         #include <sstream>
         #include <cstdlib>
 
+        #ifndef _MSC_VER
+        #if __cplusplus < 202002L
+        // C++20 earlier code
+        // https://en.cppreference.com/w/cpp/language/attributes/likely
+        #define likely(x)       __builtin_expect(!!(x), 1)
+        #define unlikely(x)     __builtin_expect(!!(x), 0)
+        #endif
+        #endif
+
         // This is defined in guards.cpp so we don't need to import PyTorch headers that are slooow.
         // We manually link it below to workaround issues with fbcode build.
         static void* (*_torchinductor_pyobject_tensor_data_ptr)(PyObject* obj);