Make tests run in serial as they break in parallel

It would be nice to fix them in parallel but I lack the time.

Author: chewi

configure.ac

@@ -1,7 +1,7 @@
 AC_INIT([patchelf], m4_esyscmd([printf $(cat ./version)]))
 AC_CONFIG_SRCDIR([src/patchelf.cc])
 AC_CONFIG_AUX_DIR([build-aux])
-AM_INIT_AUTOMAKE([-Wall -Werror dist-bzip2 foreign color-tests parallel-tests])
+AM_INIT_AUTOMAKE([-Wall -Werror dist-bzip2 foreign color-tests serial-tests])
 
 AM_PROG_CC_C_O
 AC_PROG_CXX