Configure LLVM to use js backend

Initialize the asmjs backend for LLVM

Author: badboy

src/bootstrap/native.rs

@@ -65,7 +65,7 @@ pub fn llvm(build: &Build, target: &str) {
        .out_dir(&dst)
        .profile(if build.config.llvm_optimize {"Release"} else {"Debug"})
        .define("LLVM_ENABLE_ASSERTIONS", assertions)
-       .define("LLVM_TARGETS_TO_BUILD", "X86;ARM;AArch64;Mips;PowerPC;SystemZ")
+       .define("LLVM_TARGETS_TO_BUILD", "X86;ARM;AArch64;Mips;PowerPC;SystemZ;JSBackend")
        .define("LLVM_INCLUDE_EXAMPLES", "OFF")
        .define("LLVM_INCLUDE_TESTS", "OFF")
        .define("LLVM_INCLUDE_DOCS", "OFF")

src/librustc_llvm/lib.rs

@@ -434,6 +434,10 @@ pub fn initialize_available_targets() {
                  LLVMInitializeSystemZTargetMC,
                  LLVMInitializeSystemZAsmPrinter,
                  LLVMInitializeSystemZAsmParser);
+    init_target!(llvm_component = "jsbackend",
+                 LLVMInitializeJSBackendTargetInfo,
+                 LLVMInitializeJSBackendTarget,
+                 LLVMInitializeJSBackendTargetMC);
 }
 
 pub fn last_error() -> Option<String> {