Drop references to NIX_MANFIESTS_DIR and NIX_BUILD_HOOK

Dependencies

• [2] PWU6YAQA add NIX_MANIFESTS_DIR to tests
• [3] UIA3ULNU Give each test its own Nix directories
• [4] FAIJDQKZ
• [5] LAJHRL6O Fix tests
• [6] PVBTVPKJ nix needs env vars as absolute paths
• [7] 4WLW4VHS Test setup: support arbitrary hydra config
• [8] N3KBVX6G Set $PERL5LIB properly in hydra-init in "make check"
• [9] 3HRBFWGK tests: change postgresql socket dir to /tmp
• [10] OWRS526H Create an ephemeral PostgreSQL database per test
• [11] HX4QYOYA add first evaluations tests
• [12] JRVI4XTV tests: Use $(builddir) instead of `pwd`.
• [13] OB7GB5DL Test environment cleanups
• [14] GAZHOBWE Better fix
• [*] G2ZB6464 first test, not yet in buildprocess

Change contents

• edit in t/Makefile.am at line 11
  [4.91]→[2.0:62](∅→∅)
  − NIX_MANIFESTS_DIR="$(abs_builddir)/nix/var/nix/manifests" \
• edit in t/Makefile.am at line 13
  [4.190]→[4.0:24](∅→∅)
  − NIX_BUILD_HOOK= \
• edit in t/lib/Setup.pm at line 59
  [3.1942]→[4.764:765](∅→∅),[4.764]→[4.764:765](∅→∅),[4.765]→[3.1943:2005](∅→∅)
  −

  − $ENV{'NIX_MANIFESTS_DIR'} = "$dir/nix/var/nix/manifests";