Enhance digital synthesis in pe_synth.h with constant node detection and evaluation improvements

- Introduced a mechanism to detect constant nodes produced by unnamed INPUT models, improving synthesis accuracy.
- Updated the evaluation logic to utilize constant values, enhancing performance and reducing unnecessary computations.
- Refactored the mask computation and cone building functions for better clarity and efficiency.
- Updated `README.md` with new CMake configuration options for improved CUDA support during the build process.

Author: MacroModel

include/phy_engine/verilog/digital/README.md

@@ -154,7 +154,7 @@ The optimization pipeline supports LLVM/GCC-like levels via `pe_synth_options::o
     - Recommended optimized build settings (important for `-Omax/-Ocuda` runtime):
       - `-DCMAKE_BUILD_TYPE=Release` (or `RelWithDebInfo` for profiling)
       - `-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON` (LTO, if supported by your toolchain)
-    - `cmake -S src -B build_cuda -DCMAKE_CXX_COMPILER=clang++ -DPHY_ENGINE_ENABLE_CUDA_PE_SYNTH=ON -DPHY_ENGINE_CUDA_PATH=/usr/local/cuda -DPHY_ENGINE_CUDA_PE_SYNTH_ARCH=sm_70`
+    - `cmake -S src -B build_cuda -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DPHY_ENGINE_ENABLE_CUDA_PE_SYNTH=ON -DPHY_ENGINE_CUDA_PATH=/usr/local/cuda -DPHY_ENGINE_CUDA_PE_SYNTH_ARCH=sm_70 -DCMAKE_EXE_LINKER_FLAGS="-fuse-ld=lld" -DCMAKE_SHARED_LINKER_FLAGS="-fuse-ld=lld" `
     - `cmake --build build_cuda -j`
   - Run example (2x V100 -> mask 3):
     - `./build_cuda/verilog2plsav out.sav in.v -Ocuda --cuda-device-mask 3`