Make ssl certificate for ssl_passphrase_callback test via Makefile

The recipe was previously given in comments in the module's test
script, but now we have an explicit recipe in the Makefile. The now
redundant comments in the script are removed.

This recipe shouldn't be needed in normal use, as the certificate and
key are in git and don't need to be regenerated.

Discussion: https://postgr.es/m/ae8f21fc-95cb-c98a-f241-1936133f466f@2ndQuadrant.com

src/test/modules/ssl_passphrase_callback/Makefile

@@ -20,3 +20,21 @@ include $(top_srcdir)/contrib/contrib-global.mk
 endif
 
 SHLIB_LINK += $(filter -lssl -lcrypto -lssleay32 -leay32, $(LIBS))
+
+# Targets to generate or remove the ssl certificate and key
+# Normally not needed. Don't run these targets in a vpath build, the results
+# won't be in the right place if you do.
+
+# needs to agree with what's in the test script
+PASS = FooBaR1
+
+.PHONY: ssl-files ssl-files-clean
+
+ssl-files:
+	openssl req -new -x509 -days 10000 -nodes -out server.crt \
+		-keyout server.ckey -subj "/CN=localhost"
+	openssl rsa -aes256 -in server.ckey -out server.key -passout pass:$(PASS)
+	rm server.ckey
+
+ssl-files-clean:
+	rm -f server.crt server.key

src/test/modules/ssl_passphrase_callback/t/001_testfunc.pl

@@ -15,12 +15,7 @@ unless (($ENV{with_openssl} || 'no') eq 'yes')
 my $clearpass = "FooBaR1";
 my $rot13pass = "SbbOnE1";
 
-# self-signed cert was generated like this:
-# system('openssl req -new -x509 -days 10000 -nodes -out server.crt -keyout server.ckey -subj "/CN=localhost"');
-# add the cleartext passphrase to the key, remove the unprotected key
-# system("openssl rsa -aes256 -in server.ckey -out server.key -passout pass:$clearpass");
-# unlink "server.ckey";
-
+# see the Makefile for how the certificate and key have been generated
 
 my $node = get_new_node('main');
 $node->init;