Fix build crash on Clang by isolating lp_solve C flags

[Mohit-Lakra]

I ran into a build failure while trying to run some of the volume examples on my machine using Clang. It turns out that lp_solve (which is pure C) was accidentally trying to use the project-wide C++17 flags. Clang is pretty strict about this and throws an error because -std=c++17 isn't valid for C files.

I’ve updated LPSolve.cmake to make sure the lp_solve target is strictly treated as C.

What I changed:

Forced the LINKER_LANGUAGE to C for the lp_solve target.

Set the C_STANDARD to 99 so it doesn't try to inherit the C++ standard.

Added a generator expression to the compile options so that -std=c99 is only applied to C files. This effectively "shields" the dependency from any C++ flag leakage.

This should make the build process much smoother for anyone working on macOS or using newer versions of Clang.

Fixes: #440

Before :

After :

[Mohit-Lakra]

Hi @vissarion , I've implemented a fix for the build crash we were seeing on Clang. It specifically isolates the lp_solve C dependency so it doesn't try to use the project's C++17 flags. I verified the fix by building the hpolytopeVolume example, and it's working smoothly now. Please review it whenever you have time!