support/dependencies: treat BSD-tar like the other cases

Currently, when we detect that tar is BSD-tar, we fake an unsupported
version (major, minor) and rely on the version check to reject BSD-tar.

There is no reason to use such shenanigans, when we can simply reject it
from the onset.

Simplify the logic:
  - use positive logic in the condition
  - directly exit in error

Also, comment that case like the other cases are commented.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/dependencies/check-host-tar.sh

@@ -20,10 +20,11 @@ major=`echo "$version" | cut -d. -f1`
 minor=`echo "$version" | cut -d. -f2`
 bugfix=`echo "$version" | cut -d. -f3`
 version_bsd=`$tar --version | grep 'bsdtar'`
-if [ ! -z "${version_bsd}" ] ; then 
-  # mark as invalid version - not all command line options are available
-  major=0
-  minor=0
+
+# BSD tar does not have all the command-line options
+if [ -n "${version_bsd}" ] ; then
+    # echo nothing: no suitable tar found
+    exit 1
 fi
 
 # Minimal version = 1.27 (previous versions do not correctly unpack archives