tests: fix tests build (LDFLAGS_GNUHASH not longer defined)

Since commit a899b909, variable LDFLAGS_GNUHASH has been replaced
by CFLAG_-Wl--hash-style=gnu. This change has not been reported to
the tests buildsys.

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

test/Rules.mak

@@ -94,7 +94,7 @@ endif
 
 ifeq ($(LDSO_GNU_HASH_SUPPORT),y)
 # Check for binutils support is done on root Rules.mak
-LDFLAGS += -Wl,${LDFLAGS_GNUHASH}
+LDFLAGS += $(CFLAG_-Wl--hash-style=gnu)
 endif