Update code base to use LLVM 21

crates/llvm-builder/README.md

@@ -82,10 +82,10 @@ Obtain a compatible build for your host platform from the release section of thi
 
       Build artifacts end up in the `./target-llvm/gnu/target-final/` directory by default.
       The `gnu` directory depends on the supported archticture and will either be `gnu`, `musl` or `emscripten`.
-      You now need to export the final target directory `$LLVM_SYS_181_PREFIX`:
+      You now need to export the final target directory `$LLVM_SYS_211_PREFIX`:
 
       ```shell
-      export LLVM_SYS_181_PREFIX=${PWD}/target-llvm/gnu/target-final
+      export LLVM_SYS_211_PREFIX=${PWD}/target-llvm/gnu/target-final
       ```
 
       If built with the `--enable-tests` option, test tools will be in the `./target-llvm/gnu/build-final/` directory, along with copies of the build artifacts. For all supported build options, run `revive-llvm build --help`.

crates/llvm-builder/src/platforms/aarch64_linux_musl.rs

@@ -221,7 +221,6 @@ fn build_host(
                 "-DCOMPILER_RT_BUILD_MEMPROF='Off'",
                 "-DCOMPILER_RT_BUILD_ORC='Off'",
                 "-DCOMPILER_RT_DEFAULT_TARGET_ARCH='aarch64'",
-                "-DCOMPILER_RT_DEFAULT_TARGET_ONLY='On'",
             ])
             .args(crate::platforms::shared::SHARED_BUILD_OPTS)
             .args(crate::platforms::shared::shared_build_opts_ccache(

crates/llvm-builder/src/platforms/x86_64_linux_musl.rs

@@ -219,7 +219,6 @@ fn build_host(
                 "-DCOMPILER_RT_BUILD_MEMPROF='Off'",
                 "-DCOMPILER_RT_BUILD_ORC='Off'",
                 "-DCOMPILER_RT_DEFAULT_TARGET_ARCH='x86_64'",
-                "-DCOMPILER_RT_DEFAULT_TARGET_ONLY='On'",
                 "-DLIBCLANG_BUILD_STATIC='On'",
                 "-DBUILD_SHARED_LIBS='Off'",
             ])

crates/llvm-builder/src/utils.rs

@@ -38,7 +38,7 @@ pub const MUSL_SNAPSHOTS_URL: &str = "https://git.musl-libc.org/cgit/musl/snapsh
 pub const EMSDK_SOURCE_URL: &str = "https://github.com/emscripten-core/emsdk.git";
 
 /// The emscripten SDK version.
-pub const EMSDK_VERSION: &str = "4.0.9";
+pub const EMSDK_VERSION: &str = "4.0.20";
 
 /// The subprocess runner.
 ///