this equates to -ftrivial-auto-var-init=pattern
clang has removed support for -ftrivial-auto-var-init=zero and
are unlikely to re-add it, so use -ftrivial-auto-var-init=pattern
on both compilers if only to make behaviour more consistent
between the two.
add to pkgsExtraHardening's defaultHardeningFlags.
Patch every `derivation` call in the bootsrap process to add it a
conditional `__contentAddressed` parameter.
That way, passing `contentAddressedByDefault` means that the entire
build closure of a system can be content addressed
