diff --git a/mk/prefix.mk b/mk/prefix.mk
index 6bc1dfbca..b4cbce78e 100644
--- a/mk/prefix.mk
+++ b/mk/prefix.mk
@@ -12,6 +12,7 @@ LIBSTDCXX_TARGET=recipes/libs/libstdcxx-v3/target/$(TARGET)/$(HOST_TARGET)
 RELIBC_FREESTANDING_TARGET=recipes/core/relibc/target/$(TARGET)/$(HOST_TARGET)
 RELIBC_TARGET=recipes/core/relibc/target/$(TARGET)
 LLVM_TARGET=recipes/dev/llvm21/target/$(HOST_TARGET)/$(TARGET)
+LLVM_RT_TARGET=recipes/dev/llvm-rt21/target/$(TARGET)/$(HOST_TARGET)
 RUST_TARGET=recipes/dev/rust/target/$(HOST_TARGET)/$(TARGET)
 CLANG_TARGET=recipes/dev/clang21/target/$(HOST_TARGET)/$(TARGET)
 LLD_TARGET=recipes/dev/lld21/target/$(HOST_TARGET)/$(TARGET)
@@ -305,6 +306,8 @@ else
 	@#TODO: generates wrong lib path for libtool
 	rm -f "$@.partial"/$(GNU_TARGET)/lib/libstdc++.la
 	rm -f "$@.partial"/$(GNU_TARGET)/lib/libsupc++.la
+	@#TODO: Needed by clang, yet not emitted
+	ln -s crtbegin.o "$@.partial"/lib/gcc/$(GNU_TARGET)/13.2.0/crtbeginT.o
 # hosted libstdcxx
 	export PATH="$(ROOT)/$@.partial/bin:$$PATH" \
 		ACLOCAL_PATH="$(LIBTOOL_PATH)/share/aclocal:$$ACLOCAL_PATH" && \
@@ -431,7 +434,7 @@ endif
 endif
 
 # BUILD CLANG ---------------------------------------------------
-$(PREFIX)/clang-install: | $(PREFIX)/gcc-install $(FSTOOLS_TAG) $(CONTAINER_TAG)
+$(PREFIX)/clang-install: | $(PREFIX)/relibc-freestanding-install $(FSTOOLS_TAG) $(CONTAINER_TAG)
 ifeq ($(PODMAN_BUILD),1)
 	$(PODMAN_RUN) make $@
 else
@@ -446,9 +449,15 @@ else
 	cp -r "$(CLANG_TARGET)/stage/usr/". "$@.partial"
 	cp -r "$(LLD_TARGET)/stage/usr/". "$@.partial"
 	rm -rf "$@.partial/lib/"*.a
+	echo "--sysroot=$(ROOT)/$(PREFIX)/relibc-freestanding-install" > "$@.partial/bin/$(GNU_TARGET).cfg"
+	export PATH="$(LIBTOOL_PATH)/bin:$(ROOT)/$@.partial/bin:$$PATH" $(PREFIX_CONFIG) \
+		COOKBOOK_HOST_SYSROOT=/usr COOKBOOK_CROSS_TARGET=$(HOST_TARGET) REDOXER_USE_CLANG=1 && \
+		$(REPO_BIN) cook llvm-rt21
+	cp -r "$(LLVM_RT_TARGET)/stage/usr/". "$@.partial"
+	echo "--sysroot=../$(GNU_TARGET)" > "$@.partial/bin/$(GNU_TARGET).cfg"
 	mv "$@.partial" "$@"
 # no longer needed, delete build files to save disk space
-	rm -rf $(CLANG_TARGET) $(LLD_TARGET)
+	rm -rf $(CLANG_TARGET) $(LLD_TARGET) $(LLVM_RT_TARGET)
 endif
 
 endif
diff --git a/recipes/dev/clang21/recipe.toml b/recipes/dev/clang21/recipe.toml
index b5a7b3e74..6b0bf7323 100644
--- a/recipes/dev/clang21/recipe.toml
+++ b/recipes/dev/clang21/recipe.toml
@@ -34,6 +34,7 @@ COOKBOOK_CMAKE_FLAGS+=(
     -DLLVM_ENABLE_LTO=Off
     -DLLVM_ENABLE_RTTI=On
     -DLLVM_ENABLE_THREADS=On
+    -DLLVM_INCLUDE_DOCS=Off
     -DLLVM_INCLUDE_EXAMPLES=Off
     -DLLVM_INCLUDE_TESTS=Off
     -DLLVM_OPTIMIZED_TABLEGEN=On
diff --git a/recipes/dev/llvm-rt21/recipe.toml b/recipes/dev/llvm-rt21/recipe.toml
new file mode 100644
index 000000000..4ca29d9d9
--- /dev/null
+++ b/recipes/dev/llvm-rt21/recipe.toml
@@ -0,0 +1,43 @@
+[source]
+same_as = "../llvm21"
+
+[build]
+template = "custom"
+script = """
+DYNAMIC_INIT
+
+generate_cookbook_cmake_file "$COOKBOOK_HOST_TARGET" "" "$COOKBOOK_TOOLCHAIN" native.cmake
+
+COOKBOOK_CMAKE_FLAGS+=(
+    -DLLVM_ENABLE_RUNTIMES="compiler-rt;libcxx;libcxxabi"
+    -DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY
+    -DCOMPILER_RT_BUILD_ORC=OFF
+    -DCOMPILER_RT_BUILD_XRAY=OFF
+    -DCOMPILER_RT_BUILD_MEMPROF=OFF
+    -DCOMPILER_RT_BUILD_LIBFUZZER=OFF
+    -DCOMPILER_RT_BUILD_SANITIZERS=OFF
+    -DCOMPILER_RT_USE_BUILTINS_LIBRARY=ON
+    -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
+    -DLIBCXX_ENABLE_LOCALIZATION=OFF # TODO: *_l functions
+    -DLIBCXX_ENABLE_FILESYSTEM=OFF # TODO: fstream require locales
+    -DLIBCXXABI_USE_LLVM_UNWINDER=OFF # TODO: libunwind need link.h
+    -DLIBCXX_ENABLE_WIDE_CHARACTERS=OFF # TODO: wsctof, wsctold
+    -DCOMPILER_RT_INSTALL_PATH="/usr/lib/clang/21"
+
+# the shared options from llvm
+    -DCMAKE_CXX_FLAGS="--std=gnu++11"
+    -DLLVM_DEFAULT_TARGET_TRIPLE="${TARGET}"
+    -DLLVM_INCLUDE_DOCS=Off
+    -DLLVM_INCLUDE_EXAMPLES=Off
+    -DLLVM_INCLUDE_TESTS=Off
+    -DUNIX=1
+)
+
+COOKBOOK_SOURCE="$COOKBOOK_SOURCE/runtimes"
+
+COOKBOOK_CMAKE_FLAGS+=(
+    -DCROSS_TOOLCHAIN_FLAGS_NATIVE="-DCMAKE_TOOLCHAIN_FILE=$(realpath native.cmake)"
+)
+cookbook_cmake
+
+"""
diff --git a/recipes/dev/llvm21/recipe.toml b/recipes/dev/llvm21/recipe.toml
index f20d7b066..ce29e47b9 100644
--- a/recipes/dev/llvm21/recipe.toml
+++ b/recipes/dev/llvm21/recipe.toml
@@ -63,6 +63,7 @@ COOKBOOK_CMAKE_FLAGS+=(
     -DLLVM_ENABLE_LTO=Off
     -DLLVM_ENABLE_RTTI=On
     -DLLVM_ENABLE_THREADS=On
+    -DLLVM_INCLUDE_DOCS=Off
     -DLLVM_INCLUDE_EXAMPLES=Off
     -DLLVM_INCLUDE_TESTS=Off
     -DLLVM_OPTIMIZED_TABLEGEN=On
diff --git a/recipes/groups/llvm21-common/recipe.toml b/recipes/groups/llvm21-common/recipe.toml
index 0a56afd54..31327ae19 100644
--- a/recipes/groups/llvm21-common/recipe.toml
+++ b/recipes/groups/llvm21-common/recipe.toml
@@ -4,4 +4,5 @@ dependencies = [
     "llvm21",
     "llvm21.runtime",
     "lld21",
+    "llvm-rt21",
 ]
diff --git a/src/cook/script.rs b/src/cook/script.rs
index 43c327079..f1ad3cd8a 100644
--- a/src/cook/script.rs
+++ b/src/cook/script.rs
@@ -259,6 +259,15 @@ set(CMAKE_C_COMPILER clang)
 set(CMAKE_NM llvm-nm)
 set(CMAKE_RANLIB llvm-ranlib)
 EOF
+
+if [ "$target" != "$COOKBOOK_HOST_TARGET" ]; then
+cat >> $file <<EOF
+set(CMAKE_C_COMPILER_TARGET ${target})
+set(CMAKE_CXX_COMPILER_TARGET ${target})
+set(CMAKE_ASM_COMPILER_TARGET ${target})
+EOF
+fi
+
 fi
     cat >> $file <<EOF
 set(CMAKE_FIND_ROOT_PATH ${sysroot})