dejagnu: Fix typo in var

There is a typo in a previous commit that introduced src-dir-override
for DejaGnu.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

Makefile.in

@@ -274,9 +274,9 @@ SPIKE_SRC_GIT :=
 endif
 
 ifeq ($(findstring $(srcdir),$(DEJAGNU_SRCDIR)),$(srcdir))
-DEJAGNU_SRC_DIR := $(DEJAGNU_SRCDIR)/.git
+DEJAGNU_SRC_GIT := $(DEJAGNU_SRCDIR)/.git
 else
-DEJAGNU_SRC_DIR :=
+DEJAGNU_SRC_GIT :=
 endif
 
 ifneq ("$(wildcard $(GCC_SRCDIR)/.git)","")