fuse: Fix build under gcc6+

* GCC6+ will warn when you truncate potentally "too much data"
  Volume name 255. fName is 32.
* We don't think we care enough to enlarge fName?

Change-Id: I6f453ee62c856481605594b2ae5ff9ab41244bd1

src/add-ons/kernel/file_systems/userlandfs/server/fuse/Jamfile

@@ -10,6 +10,9 @@ SubDirSysHdrs [ FDirName $(userlandFSIncludes) fuse ] ;
 SubDirHdrs [ FDirName $(userlandFSIncludes) private ] ;
 SubDirHdrs [ FDirName $(userlandFSIncludes) shared ] ;
 
+# Don't warn on truncation under gcc6+
+SubDirC++Flags -Wno-format-truncation ;
+
 SEARCH_SOURCE += [ FDirName $(userlandFSTop) private ] ;
 SEARCH_SOURCE += [ FDirName $(userlandFSTop) shared ] ;