fetchmail: adjust zlib handling

fetchmail itself does not need zlib, there is no reference to it in its
source, so the "select BR2_PACKAGE_ZLIB" is not necessary. Moreover,
"zlib" was not added to FETCHMAIL_DEPENDENCIES (but was anyway in the
dependency chain through openssl).

In addition, LIBS="-lz" is only needed in static linking configurations,
to help fetchmail's configure script find OpenSSL (it doesn't use
pkg-config unfortunately).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/fetchmail/Config.in

@@ -3,7 +3,6 @@ config BR2_PACKAGE_FETCHMAIL
 	depends on BR2_USE_MMU # fork()
 	select BR2_PACKAGE_CA_CERTIFICATES
 	select BR2_PACKAGE_OPENSSL
-	select BR2_PACKAGE_ZLIB
 	help
 	  Fetchmail - the mail-retrieval daemon
 	  Client daemon to move mail from POP and IMAP to your local computer

package/fetchmail/fetchmail.mk

@@ -13,7 +13,11 @@ FETCHMAIL_LICENSE_FILES = COPYING
 FETCHMAIL_AUTORECONF = YES
 FETCHMAIL_GETTEXTIZE = YES
 
+# needed to help fetchmail detecting the availability of openssl,
+# because it doesn't use pkg-config
+ifeq ($(BR2_STATIC_LIBS),y)
 FETCHMAIL_CONF_ENV += LIBS="-lz"
+endif
 
 FETCHMAIL_CONF_OPTS = \
 	--with-ssl=$(STAGING_DIR)/usr