build: Fix formatting of mirror URLs in generated release announcement

Get rid of unnecessary blank lines between the URLs.

Signed-off-by: Tobias Klauser <[email protected]>

Misc

@@ -24,9 +24,9 @@ announcement:
  $(Q)echo -e " git clone git:https://github.com/netsniff-ng/netsniff-ng.git" >> .MAIL_MSG
  $(Q)echo -e " git checkout v$(VERSION_SHORT)\n" >> .MAIL_MSG
  $(Q)echo -e "Or via HTTP from one of our mirrors:\n" >> .MAIL_MSG
- $(Q)echo -e " http:https://pub.netsniff-ng.org/netsniff-ng/netsniff-ng-$(VERSION_SHORT).tar.gz\n" >> .MAIL_MSG
- $(Q)echo -e " http:https://mirror.distanz.ch/netsniff-ng/netsniff-ng-$(VERSION_SHORT).tar.gz\n" >> .MAIL_MSG
- $(Q)echo -e " http:https://github.com/netsniff-ng/netsniff-ng/archive/$(VERSION_SHORT).tar.gz\n" >> .MAIL_MSG
+ $(Q)echo -e " http:https://pub.netsniff-ng.org/netsniff-ng/netsniff-ng-$(VERSION_SHORT).tar.gz" >> .MAIL_MSG
+ $(Q)echo -e " http:https://mirror.distanz.ch/netsniff-ng/netsniff-ng-$(VERSION_SHORT).tar.gz" >> .MAIL_MSG
+ $(Q)echo -e " http:https://github.com/netsniff-ng/netsniff-ng/archive/v$(VERSION_SHORT).tar.gz\n" >> .MAIL_MSG
  $(Q)echo -e "The release can be verified via Git (see README):\n" >> .MAIL_MSG
  $(Q)echo -e " git tag -v v$(VERSION_SHORT)\n" >> .MAIL_MSG
  $(Q)echo -e "Major high-level changes since the last release are:\n" >> .MAIL_MSG