genmc/build: Update GenMC version (v0.15.0)

Now GenMC can be built as a standalone library, without
LLVM dependencies.

Author: michaliskok

genmc-sys/build.rs

@@ -28,7 +28,7 @@ mod downloading {
     /// The GenMC repository the we get our commit from.
     pub(crate) const GENMC_GITHUB_URL: &str = "https://github.com/MPI-SWS/genmc.git";
     /// The GenMC commit we depend on. It must be available on the specified GenMC repository.
-    pub(crate) const GENMC_COMMIT: &str = "d9527280bb99f1cef64326b1803ffd952e3880df";
+    pub(crate) const GENMC_COMMIT: &str = "4eff71d54ea7d4ceb04eb9234e1d162ba78573f7";
 
     /// Ensure that a local GenMC repo is present and set to the correct commit.
     /// Return the path of the GenMC repo and whether the checked out commit was changed.