feat: target=x86_64_v2 minimum for (some) vectorization

• Intel Nehalem is x86_64_v2, launched 2008.
• Intel Haswell is x86_64_v3, launched 2013.

x86-64-v2 (circa 2009: Nehalem and Jaguar)

  CMPXCHG16B	cmpxchg16b
  LAHF-SAHF	lahf
  POPCNT	popcnt
  SSE3		addsubpd
  SSE4_1	blendpd
  SSE4_2	pcmpestri
  SSSE3		phaddd

x86-64-v3 (circa 2015: Haswell and Excavator)

  AVX		vzeroall
  AVX2		vpermd
  BMI1		andn
  BMI2		bzhi
  F16C		vcvtph2ps
  FMA		vfmadd132pd
  LZCNT		lzcnt
  MOVBE		movbe
  OSXSAVE	xgetbv

.gitlab-ci.yml

@@ -39,6 +39,7 @@ variables:
     af74680405c931dab16c6674f9b97a32bf3f1122
     0a952f8b7bf6f70009dd5821bccbaf9170c73d07
     f050b1cf7835fd31992b020e1061c52294ff7330
+    c3e41153ac92f6ef92414024a8386d4ceec2615c
   ## Ref: https://github.com/spack/spack/commit/[hash]
   ## [hash]: [description]
   ## b5ef5c2eb5145020f9de1bcb964626ce6ac2d02e: geant4: version bumps for Geant4 11.1.0
@@ -68,6 +69,7 @@ variables:
   ## af74680405c931dab16c6674f9b97a32bf3f1122: depfile: improve tab completion
   ## 0a952f8b7bf6f70009dd5821bccbaf9170c73d07: docs updates for spack env depfile
   ## f050b1cf7835fd31992b020e1061c52294ff7330: depfile: variable with all identifiers
+  ## c3e41153ac92f6ef92414024a8386d4ceec2615c: Package requirements: allow single specs in requirement lists
 
   ## EIC spack organization and repository, e.g. eic/eic-spack
   EICSPACK_ORGREPO: "eic/eic-spack"