init incremental compilation check tool

test/incremental/hello

@@ -0,0 +1,13 @@
+#target=x86_64-linux
+#update=initial version
+#file=main.zig
+pub fn main() !void {
+    try std.io.getStdOut().writeAll("good morning\n");
+}
+#expect_stdout="good morning\n"
+#update=change the string
+#file=main.zig
+pub fn main() !void {
+    try std.io.getStdOut().writeAll("おはようございます\n");
+}
+#expect_stdout="おはようございます\n"