compiler: Updates for LLVM/Clang 20 API changes.

src/codegen/llvm.zig

@@ -1053,7 +1053,11 @@ pub const Object = struct {
             .is_small = options.is_small,
             .time_report = options.time_report,
             .tsan = options.sanitize_thread,
-            .lto = options.lto != .none,
+            .lto = switch (options.lto) {
+                .none => .None,
+                .thin => .ThinPreLink,
+                .full => .FullPreLink,
+            },
             // https://github.com/ziglang/zig/issues/21215
             .allow_fast_isel = !comp.root_mod.resolved_target.result.cpu.arch.isMIPS(),
             .asm_filename = null,

src/codegen/llvm/bindings.zig

@@ -90,7 +90,7 @@ pub const TargetMachine = opaque {
         time_report: bool,
         tsan: bool,
         sancov: bool,
-        lto: bool,
+        lto: LtoPhase,
         allow_fast_isel: bool,
         asm_filename: ?[*:0]const u8,
         bin_filename: ?[*:0]const u8,
@@ -98,6 +98,14 @@ pub const TargetMachine = opaque {
         bitcode_filename: ?[*:0]const u8,
         coverage: Coverage,
 
+        pub const LtoPhase = enum(c_int) {
+            None,
+            ThinPreLink,
+            ThinPostLink,
+            FullPreLink,
+            FullPostLink,
+        };
+
         pub const Coverage = extern struct {
             CoverageType: Coverage.Type,
             IndirectCalls: bool,