[Integrated] [foreign-jextract] RFR: Tweak JextractToolRunner to use file helper routines in FileUtils library

[Maurizio Cimadamore]

Changeset: fe531d61
Author:    Maurizio Cimadamore <mcimadamore at openjdk.org>
Date:      2020-04-07 01:09:02 +0000
URL:       https://git.openjdk.java.net/panama-foreign/commit/fe531d61

Tweak JextractToolRunner to use file helper routines in FileUtils library

Reviewed-by: henryjen

! test/jdk/tools/jextract/BadBitfieldTest.java
! test/jdk/tools/jextract/ConstantsTest.java
! test/jdk/tools/jextract/JextractToolProviderTest.java
! test/jdk/tools/jextract/JextractToolRunner.java
! test/jdk/tools/jextract/RepeatedDeclsTest.java
! test/jdk/tools/jextract/Test8240181.java
! test/jdk/tools/jextract/Test8240657.java
! test/jdk/tools/jextract/Test8240752.java
! test/jdk/tools/jextract/Test8240811.java
! test/jdk/tools/jextract/UniondeclTest.java