Don't use $(EXHEADER) directly in for loops, as most shells will break
if $(EXHEADER) is empty.

Notified by many, solution suggested by Carson Gaspar <carson@taltos.org>

crypto/ocsp/Makefile.ssl

diff --git a/crypto/ocsp/Makefile.ssl b/crypto/ocsp/Makefile.ssl
index 8a4fdc3..c4f50af 100644
--- a/crypto/ocsp/Makefile.ssl
+++ b/crypto/ocsp/Makefile.ssl
@@ -56,7 +56,7 @@
 	@$(PERL) $(TOP)/util/mklink.pl ../../apps $(APPS)
 
 install:
-	@for i in $(EXHEADER) ; \
+	@headerlist="$(EXHEADER)"; for i in $$headerlist ; \
 	do  \
 	(cp $$i $(INSTALL_PREFIX)$(INSTALLTOP)/include/openssl/$$i; \
 	chmod 644 $(INSTALL_PREFIX)$(INSTALLTOP)/include/openssl/$$i ); \