fix: support -Dtarget=[target] for release builds

Specifying a target will still produce a baseline cpu release build.

build.zig

@@ -112,11 +112,26 @@ fn build_release(
         .{ .cpu_arch = .x86_64, .os_tag = .windows },
         .{ .cpu_arch = .aarch64, .os_tag = .windows },
     } else blk: {
+        const maybe_triple = b.option(
+            []const u8,
+            "target",
+            "The CPU architecture, OS, and ABI to build for",
+        );
+        const triple = maybe_triple orelse {
             const native_target = b.resolveTargetQuery(.{}).result;
             break :blk &.{
                 .{ .cpu_arch = native_target.cpu.arch, .os_tag = native_target.os.tag },
             };
         };
+        const selected_target = std.Build.parseTargetQuery(.{
+            .arch_os_abi = triple,
+        }) catch |err| switch (err) {
+            error.ParseFailed => @panic("unknown target"),
+        };
+        break :blk &.{
+            .{ .cpu_arch = selected_target.cpu_arch, .os_tag = selected_target.os_tag, .abi = selected_target.abi },
+        };
+    };
     const optimize = b.standardOptimizeOption(.{});
     const optimize_release = optimize;
     const optimize_debug = optimize;