correct name of GNU shared libraries

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Makefile.shared

@@ -171,7 +171,7 @@ DO_GNU_DSO=\
 	$(DO_GNU_SO_COMMON)
 DO_GNU_SO=\
 	$(CALC_VERSIONS); \
-	SHLIB=lib$$SHLIB; \
+	SHLIB=lib$(LIBNAME).so; \
 	ALLSYMSFLAGS='-Wl,--whole-archive'; \
 	NOALLSYMSFLAGS='-Wl,--no-whole-archive'; \
 	$(DO_GNU_SO_COMMON)