Makefile: NO_OPENSSL=1 should no longer imply BLK_SHA1=1

Use the collision detecting SHA-1 implementation by default even when
NO_OPENSSL is set.

Setting NO_OPENSSL=UnfortunatelyYes has implied BLK_SHA1=1 ever since
the former was introduced in dd53c7a (Support for NO_OPENSSL,
2005-07-29).  That implication should have been removed when the
default SHA-1 implementation changed from OpenSSL to DC_SHA1 in
e6b07da (Makefile: make DC_SHA1 the default, 2017-03-17).  Finish
what that commit started by removing the BLK_SHA1 fallback setting so
the default DC_SHA1 implementation will be used.

Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: avar

Makefile

@@ -23,7 +23,6 @@ all::
 # it at all).
 #
 # Define NO_OPENSSL environment variable if you do not have OpenSSL.
-# This also implies BLK_SHA1.
 #
 # Define USE_LIBPCRE if you have and want to use libpcre. Various
 # commands such as log and grep offer runtime options to use
@@ -1260,7 +1259,6 @@ ifndef NO_OPENSSL
 	endif
 else
 	BASIC_CFLAGS += -DNO_OPENSSL
-	BLK_SHA1 = 1
 	OPENSSL_LIBSSL =
 endif
 ifdef NO_OPENSSL

configure.ac

@@ -241,7 +241,6 @@ AC_MSG_NOTICE([CHECKS for site configuration])
 # a bundled SHA1 routine optimized for PowerPC.
 #
 # Define NO_OPENSSL environment variable if you do not have OpenSSL.
-# This also implies BLK_SHA1.
 #
 # Define OPENSSLDIR=/foo/bar if your openssl header and library files are in
 # /foo/bar/include and /foo/bar/lib directories.