fix --disable-werror

-Werror is unconditionally set since version 1.6.2 and
649e6f2
resulting in the following build failure:

In file included from /home/thomas/autobuild/instance-0/output-1/host/mips-buildroot-linux-gnu/sysroot/usr/include/bits/libc-header-start.h:33,
                 from /home/thomas/autobuild/instance-0/output-1/host/mips-buildroot-linux-gnu/sysroot/usr/include/stdlib.h:26,
                 from ./lib/stdlib.h:36,
                 from ./libtac/include/libtac.h:35,
                 from support.h:25,
                 from support.c:28:
/home/thomas/autobuild/instance-0/output-1/host/mips-buildroot-linux-gnu/sysroot/usr/include/features.h:413:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp]
  413 | #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
      |    ^~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/9b5ece5d01eac8a760ed9ca331a902d1c47387a7

Signed-off-by: Fabrice Fontaine <[email protected]>

Makefile.am

@@ -9,7 +9,11 @@
 ACLOCAL_AMFLAGS = -I config -I m4
 SUBDIRS = lib
 AUTOMAKE_OPTIONS = subdir-objects
-AM_CFLAGS = -Wall -Wextra -Werror
+AM_CFLAGS = -Wall -Wextra
+
+if ENABLE_WERROR
+AM_CFLAGS += -Werror
+endif
 
 bin_PROGRAMS = tacc
 tacc_SOURCES = tacc.c

configure.ac

@@ -16,7 +16,7 @@ See the included file: LICENSE for copyright information.
 ])
 AC_INIT([pam_tacplus],[1.7.0],[https://github.com/kravietz/pam_tacplus/issues/],[pam_tacplus],[https://github.com/kravietz/pam_tacplus/])
 AC_CONFIG_AUX_DIR(config)
-AM_INIT_AUTOMAKE([foreign -Wall -Werror])
+AM_INIT_AUTOMAKE([foreign -Wall])
 AC_CONFIG_SRCDIR([pam_tacplus.c])
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_MACRO_DIR([config])