src/print_env: print the native target

Add the native target triple to the zig env command output.

The target triple is formatted the same way as it is done in the
zig targets command.

src/print_env.zig

@@ -21,6 +21,10 @@ pub fn cmdEnv(gpa: Allocator, args: []const []const u8, stdout: std.fs.File.Writ
     const global_cache_dir = try introspect.resolveGlobalCacheDir(gpa);
     defer gpa.free(global_cache_dir);
 
+    const info = try std.zig.system.NativeTargetInfo.detect(gpa, .{});
+    const triple = try info.target.zigTriple(gpa);
+    defer gpa.free(triple);
+
     var bw = std.io.bufferedWriter(stdout);
     const w = bw.writer();
 
@@ -42,6 +46,9 @@ pub fn cmdEnv(gpa: Allocator, args: []const []const u8, stdout: std.fs.File.Writ
     try jws.objectField("version");
     try jws.emitString(build_options.version);
 
+    try jws.objectField("target");
+    try jws.emitString(triple);
+
     try jws.endObject();
     try w.writeByte('\n');
     try bw.flush();