Revert "contrib: sidplay2: remove cached autoconf files"

This reverts commit b409b390fb.

It seems removing the aclocal.m4 is not needed anymore.
The Makefile.in configure will be generated anyway since we run AUTORECONF.

contrib/src/sidplay2/rules.mak

@@ -38,11 +38,6 @@ sidplay-libs: sidplay-libs-$(SID_VERSION).tar.gz .sum-sidplay2
 
 .sidplay2: sidplay-libs
 	$(REQUIRE_GPL)
-	for d in . libsidplay builders resid builders/resid-builder \
-			builders/hardsid-builder libsidutils ; \
-	do \
-		(cd $</$$d && rm -rf aclocal.m4 Makefile.in configure) || exit $$? ; \
-	done
 	for d in . libsidplay resid builders/resid-builder \
 			builders/hardsid-builder libsidutils ; \
 	do \