xml indentation issue

[ChristinaXu2017]

Describe the bug
some qsignature unit test failed in Eclipse, because the output look like:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<qsignature>
    <files>
        <file coverage="4" id="1" name="/var/folders/df/jjbl15r1537868_k4cvl3wxjnt65fc/T/junit1426580825586087499/bespoke.qsig.vcf"/>
        <file coverage="7" id="2" name="/var/folders/df/jjbl15r1537868_k4cvl3wxjnt65fc/T/junit1426580825586087499/traditional.qsig.vcf"/>
    </files>
    ...
</qsignature>

To Reproduce
the reason is still under investigation, it more likely caused by XML writer library: javax.xml.transform.

Expected behavior
The expected output is without indent as run on the terminal by Gradle command

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<qsignature>
<files>
<file coverage="4" id="1" name="/var/folders/df/jjbl15r1537868_k4cvl3wxjnt65fc/T/junit2515560971504011429/bespoke.qsig.vcf"/>
<file coverage="7" id="2" name="/var/folders/df/jjbl15r1537868_k4cvl3wxjnt65fc/T/junit2515560971504011429/traditional.qsig.vcf"/>
</files>
...
</qsignature>

Desktop (please complete the following information):

• OS: mac
• Version java8

Additional context
Add any other context about the problem here.