curl: disable libssh2 support

Otherwise internal curl may pick up system libssh2.

curl/makefile.mk

@@ -84,7 +84,7 @@ CONFIGURE_FLAGS=--disable-shared
 .ELSE
 CONFIGURE_FLAGS=--disable-static
 .ENDIF
-CONFIGURE_FLAGS+= --without-ssl --without-libidn --enable-ftp --enable-ipv6 --enable-http --disable-gopher --disable-file --disable-ldap --disable-telnet --disable-dict CPPFLAGS="$(curl_CFLAGS)"  LDFLAGS="$(curl_LDFLAGS)"
+CONFIGURE_FLAGS+= --without-ssl --without-libidn --enable-ftp --enable-ipv6 --enable-http --disable-gopher --disable-file --disable-ldap --disable-telnet --disable-dict --without-libssh2 CPPFLAGS="$(curl_CFLAGS)"  LDFLAGS="$(curl_LDFLAGS)"
 
 .IF "$(CROSS_COMPILING)"=="YES"
 CONFIGURE_FLAGS+=--build=$(BUILD_PLATFORM) --host=$(HOST_PLATFORM)