Bug#1021082: bash: missing BINDNOW build hardening

[Christian Göttsche]

Source: bash
Version: 5.2-1

Bash is not build with the hardening option BINDNOW[1], i.e. the
linker flag `-z now` is missing.

[1]: 
https://wiki.debian.org/Hardening#DEB_BUILD_HARDENING_BINDNOW_.28ld_-z_now.29