Pass no-verify-fixpoint option to instcombine in LLVM 18

When LLVM 18 is used, pass the no-verify-fixpoint option when
running the instcombine pass. Otherwise LLVM may abort with an
error.

The background here is that this option is enabled by default for
testing purposes, because instcombine is normally only explicitly
invoked like this inside tests. If it is used in an actual
production pipeline, the no-verify-fixpoint option needs to be
enabled.

This should fix the issue reported at
https://bugzilla.redhat.com/show_bug.cgi?id=2268800.

Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28101>

src/gallium/auxiliary/gallivm/lp_bld_init.c

@@ -609,7 +609,11 @@ gallivm_compile_module(struct gallivm_state *gallivm)
    LLVMRunPasses(gallivm->module, passes, LLVMGetExecutionEngineTargetMachine(gallivm->engine), opts);
 
    if (!(gallivm_perf & GALLIVM_PERF_NO_OPT))
+#if LLVM_VERSION_MAJOR >= 18
+      strcpy(passes, "sroa,early-cse,simplifycfg,reassociate,mem2reg,instsimplify,instcombine<no-verify-fixpoint>");
+#else
       strcpy(passes, "sroa,early-cse,simplifycfg,reassociate,mem2reg,instsimplify,instcombine");
+#endif
    else
       strcpy(passes, "mem2reg");