Build: Require Automake 1.12 and use serial-tests option.
It should actually still work with Automake 1.10 if
the serial-tests option is removed. Automake 1.13 started
using parallel tests by default and the option to get
the old behavior isn't supported before 1.12.
At least for now, parallel tests don't improve anything
in XZ Utils but they hide the progress output from
test_compress.sh.
diff --git a/configure.ac b/configure.ac
index b52eb66..97dfb27 100644
--- a/configure.ac
+++ b/configure.ac
@@ -443,7 +443,9 @@
echo
echo "Initializing Automake:"
-AM_INIT_AUTOMAKE([1.10 foreign tar-v7 filename-length-max=99])
+# Automake 1.10 should still be enough but you need to omit serial-tests.
+dnl AM_INIT_AUTOMAKE([1.10 foreign tar-v7 filename-length-max=99])
+AM_INIT_AUTOMAKE([1.12 foreign tar-v7 filename-length-max=99 serial-tests])
AC_PROG_LN_S
AC_PROG_CC_C99
