test_librt: Fix build system for shm_open/unlink tests

Fix and align build system of librt tests to the test suite.

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

test/librt/Makefile

@@ -5,5 +5,3 @@ top_builddir=../../
 include ../Rules.mak
 -include Makefile.in
 include ../Test.mak
-
-LDFLAGS_shmtest := -lrt

test/librt/Makefile.in

@@ -0,0 +1,4 @@
+# uClibc shm tests
+# Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+
+LDFLAGS_shmtest := -lrt