libgcrypt is required when --with-gnutls specified explicitly

We must use --with-gnutls option to select explicitly the GnuTLS library over OpenSSL. Currently if we specify --with-gnutls option and libgcrypt header file is not installed, we will have the following error.

(... we assume courier-authlib is already installed on /home/mumumu/local )

$ sh INSTALLME courier-imap https://github.com/svarshavchik/courier-libs.git
$ cd courier-imap
$ COURIERAUTHCONFIG=/home/mumumu/local/bin/courierauthconfig CFLAGS=-I/home/mumumu/local/include ./configure --prefix=/home/mumumu/local/ --with-gnutls
$ make -j8

(.snip)

/bin/bash ./libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I.   -I/usr/include/p11-kit-1  -I./.. -I.. -I./../.. -I../.. -Wall -I/home/mumumu/local/include -MT tlspasswordcache.lo -MD -MP -MF .deps/tlspasswordcache.Tpo -c -o tlspasswordcache.lo tlspasswordcache.c

mv -f .deps/tcpdaccess.Tpo .deps/tcpdaccess.Po
tlspasswordcache.c:366:9: error: unknown type name ‘EVP_CIPHER_CTX’
 typedef EVP_CIPHER_CTX CIPHER_CONTEXT;
         ^~~~~~~~~~~~~~
Makefile:577: recipe for target 'tlspasswordcache.lo' failed
make[3]: *** [tlspasswordcache.lo] Error 1

Yes, libgcrypt is required when --with-gnutls option specified explicitly, but this fact is not forced by configure script, we should change configure.ac to enforce its requirement.

svarshavchik / courier-libs

libgcrypt is required when --with-gnutls specified explicitly #11