Try resolve regular build errors caused by IOException

The exception happens at tear down where we try to delete all files. One
reason could be that the file doesn't exist anymore. Thus, we try to add
the flag SKIP_MISSING when recursively deleting files.

java.io.IOException: Could not delete file
/jobs/genie.papyrus/Papyrus-Compare-Oxygen-Nightly/workspace/sources/plugins/compare/tests/org.eclipse.papyrus.compare.diagram.tests.git/target/work/data/repo/.git/gc.log.lock
	at org.eclipse.jgit.util.FileUtils.delete(FileUtils.java:217)
	at org.eclipse.jgit.util.FileUtils.delete(FileUtils.java:184)
	at org.eclipse.jgit.util.FileUtils.delete(FileUtils.java:186)

Change-Id: Ia8d2ef29ebcee189ab3affb7ebe17c67c142e065
Signed-off-by: Philip Langer <planger@eclipsesource.com>
diff --git a/plugins/compare/tests/org.eclipse.papyrus.compare.diagram.tests.git/src/org/eclipse/papyrus/compare/diagram/tests/egit/AbstractGitMergeTestCase.java b/plugins/compare/tests/org.eclipse.papyrus.compare.diagram.tests.git/src/org/eclipse/papyrus/compare/diagram/tests/egit/AbstractGitMergeTestCase.java
index 1176870..4c102ef 100644
--- a/plugins/compare/tests/org.eclipse.papyrus.compare.diagram.tests.git/src/org/eclipse/papyrus/compare/diagram/tests/egit/AbstractGitMergeTestCase.java
+++ b/plugins/compare/tests/org.eclipse.papyrus.compare.diagram.tests.git/src/org/eclipse/papyrus/compare/diagram/tests/egit/AbstractGitMergeTestCase.java
@@ -159,7 +159,7 @@
 		if (gitDir.exists()) {
 			File gitRoot = gitDir.getParentFile();
 			if (gitRoot.exists()) {
-				FileUtils.delete(gitRoot, FileUtils.RECURSIVE | FileUtils.RETRY);
+				FileUtils.delete(gitRoot, FileUtils.RECURSIVE | FileUtils.RETRY | FileUtils.SKIP_MISSING);
 			}
 		}
 	}