Set EXE_EXT environment variable when testing

When cross compiling, we may end up with someting like apps/openssl.exe
and a number of test/*.exe.  However, util/shlib_wrap.sh doesn't know
what the executable extension should be, if any, so we need to make
sure it has access to that information when testing, since
OpenSSL::Test uses that script to execute all programs.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Configurations/unix-Makefile.tmpl

@@ -158,6 +158,7 @@ test tests: build_tests build_apps build_engines rehash
 	( cd test; \
 	  SRCTOP=../$(SRCDIR) \
 	  BLDTOP=../$(BLDDIR) \
+	  EXE_EXT=$(EXE_EXT) \
 	    $(PERL) ../$(SRCDIR)/test/run_tests.pl $(TESTS) )
 
 list-tests: