Faster linux zig build (#23075)

### What does this PR do?

### How did you verify your code works?

build.zig

@@ -68,6 +68,7 @@ const BunBuildOptions = struct {
 
     cached_options_module: ?*Module = null,
     windows_shim: ?WindowsShim = null,
+    llvm_codegen_threads: ?u32 = null,
 
     pub fn isBaseline(this: *const BunBuildOptions) bool {
         return this.arch.isX86() and
@@ -269,6 +270,7 @@ pub fn build(b: *Build) !void {
         .enable_logs = b.option(bool, "enable_logs", "Enable logs in release") orelse false,
         .enable_asan = b.option(bool, "enable_asan", "Enable asan") orelse false,
         .enable_valgrind = b.option(bool, "enable_valgrind", "Enable valgrind") orelse false,
+        .llvm_codegen_threads = b.option(u32, "llvm_codegen_threads", "Number of threads to use for LLVM codegen") orelse 1,
     };
 
     // zig build obj
@@ -603,7 +605,15 @@ fn configureObj(b: *Build, opts: *BunBuildOptions, obj: *Compile) void {
 
     // Object options
     obj.use_llvm = !opts.no_llvm;
-    obj.use_lld = if (opts.os == .mac) false else !opts.no_llvm;
+    obj.use_lld = if (opts.os == .mac or opts.os == .linux) false else !opts.no_llvm;
+
+    if (opts.optimize == .Debug) {
+        if (@hasField(std.meta.Child(@TypeOf(obj)), "llvm_codegen_threads"))
+            obj.llvm_codegen_threads = opts.llvm_codegen_threads orelse 0;
+    }
+
+    obj.no_link_obj = true;
+
     if (opts.enable_asan and !enableFastBuild(b)) {
         if (@hasField(Build.Module, "sanitize_address")) {
             obj.root_module.sanitize_address = true;

cmake/targets/BuildBun.cmake

@@ -44,6 +44,14 @@ else()
   set(CONFIGURE_DEPENDS "")
 endif()
 
+set(LLVM_ZIG_CODEGEN_THREADS 0)
+# This makes the build slower, so we turn it off for now.
+# if (DEBUG)
+#   include(ProcessorCount)
+#   ProcessorCount(CPU_COUNT)
+#   set(LLVM_ZIG_CODEGEN_THREADS ${CPU_COUNT})
+# endif()
+
 # --- Dependencies ---
 
 set(BUN_DEPENDENCIES
@@ -578,7 +586,13 @@ if (TEST)
   set(BUN_ZIG_OUTPUT ${BUILD_PATH}/bun-test.o)
   set(ZIG_STEPS test)
 else()
-  set(BUN_ZIG_OUTPUT ${BUILD_PATH}/bun-zig.o)
+  if (LLVM_ZIG_CODEGEN_THREADS GREATER 1)
+    foreach(i RANGE ${LLVM_ZIG_CODEGEN_THREADS})
+      list(APPEND BUN_ZIG_OUTPUT ${BUILD_PATH}/bun-zig.${i}.o)
+    endforeach()
+  else()
+    set(BUN_ZIG_OUTPUT ${BUILD_PATH}/bun-zig.o)
+  endif()
   set(ZIG_STEPS obj)
 endif()
 
@@ -622,6 +636,7 @@ register_command(
       -Denable_logs=$<IF:$<BOOL:${ENABLE_LOGS}>,true,false>
       -Denable_asan=$<IF:$<BOOL:${ENABLE_ZIG_ASAN}>,true,false>
       -Denable_valgrind=$<IF:$<BOOL:${ENABLE_VALGRIND}>,true,false>
+      -Dllvm_codegen_threads=${LLVM_ZIG_CODEGEN_THREADS}
       -Dversion=${VERSION}
       -Dreported_nodejs_version=${NODEJS_VERSION}
       -Dcanary=${CANARY_REVISION}

cmake/tools/SetupZig.cmake

@@ -20,7 +20,7 @@ else()
   unsupported(CMAKE_SYSTEM_NAME)
 endif()
 
-set(ZIG_COMMIT "e0b7c318f318196c5f81fdf3423816a7b5bb3112")
+set(ZIG_COMMIT "55fdbfa0c86be86b68d43a4ba761e6909eb0d7b2")
 optionx(ZIG_TARGET STRING "The zig target to use" DEFAULT ${DEFAULT_ZIG_TARGET})
 
 if(CMAKE_BUILD_TYPE STREQUAL "Release")