regress: add test for empty tuple buffer overflow issue

Makefile.am

@@ -92,6 +92,7 @@ EXTRA_DIST =	pkg.m4 \
 		tests/lib1/requires-internal-missing.pc \
 		tests/lib1/requires-internal-collision.pc \
 		tests/lib1/tuple-quoting.pc \
+		tests/lib1/empty-tuple.pc \
 		tests/test_env.sh \
 		$(test_scripts) \
 		doc/conf.py \

tests/lib1/empty-tuple.pc

@@ -0,0 +1,6 @@
+xcflags=
+
+Name: empty-tuple
+Description: testing file
+Version: 1
+CFlags: ${xcflags}

tests/regress.sh

@@ -28,7 +28,8 @@ tests_init \
 	fragment_collision \
 	malformed_1 \
 	malformed_quoting \
-	explicit_sysroot
+	explicit_sysroot \
+	empty_tuple
 
 case_sensitivity_body()
 {
@@ -247,3 +248,9 @@ explicit_sysroot_body()
 	atf_check -o inline:"/sysroot/usr/share/test\n" \
 		pkgconf --with-path="${selfdir}/lib1" --variable=pkgdatadir explicit-sysroot
 }
+
+empty_tuple_body()
+{
+	atf_check -o inline:"\n" \
+		pkgconf --with-path="${selfdir}/lib1" --cflags empty-tuple
+}