Try

Author: ZuseZ4

src/bootstrap/src/core/build_steps/llvm.rs

@@ -1035,7 +1035,11 @@ impl Step for OmpOffload {
                 let inc_dir = base.display();
                 cflags.push_all(format!(" -I {inc_dir}"));
             }
+            cflags.push_all(
+                " -ULIBC_NAMESPACE -DLIBC_NAMESPACE=__llvm_libc_22_1_0_rust1_95_0nightly",
+            );
 
+            //let mytarget = TargetSelection::from_user(omp_target);
             configure_cmake(builder, target, &mut cfg, true, LdFlags::default(), cflags, &[]);
 
             // Re-use the same flags as llvm to control the level of debug information
@@ -1055,24 +1059,28 @@ impl Step for OmpOffload {
                 .profile(profile)
                 .env("LLVM_CONFIG_REAL", &host_llvm_config)
                 .define("LLVM_ENABLE_ASSERTIONS", "ON")
-                //.define("LLVM_ENABLE_PER_TARGET_RUNTIME_DIR", "ON")
+                .define("LLVM_ENABLE_PER_TARGET_RUNTIME_DIR", "ON")
                 .define("LLVM_INCLUDE_TESTS", "OFF")
                 .define("OFFLOAD_INCLUDE_TESTS", "OFF")
                 .define("OPENMP_STANDALONE_BUILD", "ON")
                 .define("LLVM_ROOT", builder.llvm_out(target).join("build"))
                 .define("LLVM_DEFAULT_TARGET_TRIPLE", omp_target)
+                .define("CMAKE_CXX_COMPILER_WORKS", "TRUE")
+                .define("CMAKE_C_COMPILER_WORKS", "TRUE")
                 .define("LLVM_DIR", llvm_cmake_dir.clone());
             if let Some(p) = clang_dir.clone() {
                 cfg.define("Clang_DIR", p);
             }
             if *omp_target != *target.triple {
-                cfg.define("LLVM_ENABLE_RUNTIMES", "openmp");
-                //cfg.define("LIBC_TARGET_TRIPLE", omp_target);
-                //cfg.define("LLVM_LIBC_FULL_BUILD", "ON");
-                //cfg.define("LLVM_ENABLE_RUNTIMES", "openmp;libc");
+                //cfg.define("LLVM_ENABLE_RUNTIMES", "openmp");
+                cfg.define("LIBC_TARGET_TRIPLE", omp_target);
+                cfg.define("LLVM_USE_LINKER", "lld");
+                cfg.define("LLVM_LIBC_FULL_BUILD", "ON");
+                cfg.define("LLVM_ENABLE_RUNTIMES", "openmp;libc");
+                cfg.define("CMAKE_C_COMPILER_TARGET", omp_target);
+                cfg.define("CMAKE_CXX_COMPILER_TARGET", omp_target);
             } else {
                 // offload can't be build for GPUs, only the host
-                //cfg.define("LLVM_ENABLE_RUNTIMES", "openmp;offload;libc");
                 cfg.define("LLVM_ENABLE_RUNTIMES", "openmp;offload");
             }
             cfg.build();