Antlib support is broken with Java 9

[snicoll]

The integration tests do not pass with JDK9

[INFO] --- maven-antrun-plugin:1.7:run (antunit) @ spring-boot-antlib ---
[INFO] Executing tasks

main:
[pathconvert] /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/spring-boot-antlib-2.0.0.BUILD-SNAPSHOT.jar
  [antunit] Build File: /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/build.xml
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1. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 1)
	/*
	^
The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files
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2. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 1)
	/*
	^
The type java.lang.String cannot be resolved. It is indirectly referenced from required .class files
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3. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 1)
	/*
	^
The type java.lang.Class cannot be resolved. It is indirectly referenced from required .class files
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4. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 20)
	public class SampleApplication {
	             ^^^^^^^^^^^^^^^^^
Implicit super constructor Object() is undefined for default constructor. Must define an explicit constructor
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5. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 22)
	public static void main(String[] args) {
	                        ^^^^^^
String cannot be resolved to a type
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6. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 23)
	System.out.println(LocalDate.class.getSimpleName());
	^^^^^^
System cannot be resolved
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7. ERROR in /Users/snicoll/workspace/pivotal/spring-boot/spring-boot-tools/spring-boot-antlib/target/it/sample/src/main/java/org/test/SampleApplication.java (at line 23)
	System.out.println(LocalDate.class.getSimpleName());
	                   ^^^^^^^^^^^^^^^
Class cannot be resolved to a type
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7 problems (7 errors)
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[snicoll]

Duplicate of #10021