Add the various testsuite runners to TESTS variable and have make call
them with RUN_FULL_TESTSUITE=1 env var.

Most of the test suites require privileged execution, 'make distcheck'
usually doesn't and probably shouldn't. Assuming the latter is used
during the release process, it may even not run on a machine which is up
to date enough to generate meaningful test suite results. Hence spare
the release process from the likely pointless delay imposed by 'make
check' by keeping TESTS variable empty when in a distcheck environment.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
Changes since v1:
- Add an internal configure option set by the distcheck target when
  building the project
- Have this configure option define BUILD_DISTCHECK automake variable
- Leave TESTS empty if BUILD_DISTCHECK is set to avoid test suite runs
  with 'make distcheck'
---
 Makefile.am  | 10 ++++++++++
 configure.ac |  5 +++++
 2 files changed, 15 insertions(+)

diff --git a/Makefile.am b/Makefile.am
index 5190a49ae69f1..f65e8d51b501e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -23,6 +23,7 @@ libnftables_LIBVERSION = 2:0:1
 ###############################################################################
 
 ACLOCAL_AMFLAGS = -I m4
+AM_DISTCHECK_CONFIGURE_FLAGS = --enable-distcheck
 
 EXTRA_DIST =
 BUILT_SOURCES =
@@ -429,3 +430,12 @@ doc_DATA = files/nftables/main.nft
 tools/nftables.service: tools/nftables.service.in ${top_builddir}/config.status
 	${AM_V_GEN}${MKDIR_P} tools
 	${AM_V_at}sed -e 's|@''sbindir''@|${sbindir}|g;s|@''pkgsysconfdir''@|${pkgsysconfdir}|g' <${srcdir}/tools/nftables.service.in >$@
+
+AM_TESTS_ENVIRONMENT = RUN_FULL_TESTSUITE=1; export RUN_FULL_TESTSUITE;
+if !BUILD_DISTCHECK
+TESTS = tests/build/run-tests.sh \
+	tests/json_echo/run-test.py \
+	tests/monitor/run-tests.sh \
+	tests/py/nft-test.py \
+	tests/shell/run-tests.sh
+endif
diff --git a/configure.ac b/configure.ac
index da16a6e257c91..8073d4d8193e2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -155,6 +155,11 @@ AC_CONFIG_COMMANDS([nftversion.h], [
 AC_SUBST([MAKE_STAMP], ["\$(shell date +%s)"])
 CFLAGS="${CFLAGS} -DMAKE_STAMP=\${MAKE_STAMP}"
 
+AC_ARG_ENABLE([distcheck],
+	      AS_HELP_STRING([--enable-distcheck], [Build for distcheck]),
+	      [enable_distcheck=yes], [])
+AM_CONDITIONAL([BUILD_DISTCHECK], [test "x$enable_distcheck" = "xyes"])
+
 AC_CONFIG_FILES([					\
 		Makefile				\
 		libnftables.pc				\
-- 
2.51.0