From Rafal Lalik:

make sure the so version is correctly set in out of source builds.
Fixes issue 89877.


git-svn-id: http://root.cern.ch/svn/root/trunk@42505 27541ba8-7e3a-0410-8455-c3a389f83636

configure

@@ -2033,9 +2033,9 @@ fi
 #
 if test "x$enable_soversion" = "xyes"; then
     logmsg "Enabling version numbers in so names"
-    major=`sed 's|\(.*\)\..*/.*|\1|' < build/version_number`
-    minor=`sed 's|.*\.\(.*\)/.*|\1|' < build/version_number`
-    revis=`sed 's|.*\..*/\([0-9]*\).*|\1|' < build/version_number`
+    major=`sed 's|\(.*\)\..*/.*|\1|' < ${ac_srcdir}/build/version_number`
+    minor=`sed 's|.*\.\(.*\)/.*|\1|' < ${ac_srcdir}/build/version_number`
+    revis=`sed 's|.*\..*/\([0-9]*\).*|\1|' < ${ac_srcdir}/build/version_number`
 
     mkliboption="-v $major $minor $revis "
     unset major