GHDL build fails on Ubuntu 25.10 due to LLVM 20 incompatibility

[RISHABH12005]

System Information

• OS: Ubuntu 25.10 (64-bit)
• eSim Version: 2.5
• Installation Script: install-eSim.sh
• Component: NGHDL / GHDL
• Environment: Oracle VirtualBox 7.2.4

Description

While installing eSim 2.5 on Ubuntu 25.10, the installation fails during the NGHDL setup phase when building GHDL. The installer aborts during the configuration step.

Steps to Reproduce

1. Clone the eSim repository
2. Run ./install-eSim.sh --install
3. Continue with default options
4. Installation fails during GHDL configuration

Error Output

Expected Behavior

The installer should either select a supported LLVM version automatically or notify the user about LLVM incompatibility and suggest a compatible version.

Analysis

Ubuntu 25.10 ships with LLVM 20 by default. GHDL 4.1.0 does not currently support LLVM 20. Even after installing LLVM 17 manually, the build process continues to invoke the default llvm-config, which corresponds to LLVM 20. This suggests that the installer does not explicitly enforce a supported LLVM version.

Attempts Made

• Installed LLVM 17 manually
• Verified availability of llvm-config-17
• Investigated installer scripts related to GHDL configuration
• Attempted to override LLVM selection using environment variables

Current Status

This issue remains unresolved and appears to require changes in the installer or upstream GHDL support for newer LLVM versions.