scons: always generate sim/tags.cc
scons: always generate sim/tags.cc

Due to insufficient build deps, the checkpoint tags might not get
updated; this commit solves this. Due to the uncommon nature of the
build target, regenerating tags.cc is a fairly clean solution. Since
SCons hashes file contents, it won't recompile anything unless a new
checkpoint upgrader is actually added.

--HG--
extra : amend_source : ed3879da7668554693f697076deaf5029cc9b954

qizenguf/MLC-STT,qizenguf/MLC-STT,HwisooSo/gemV-update,SanchayanMaity/gem5,rjschof/gem5,rallylee/gem5,TUD-OS/gem5-dtu,gem5/gem5,KuroeKurose/gem5,SanchayanMaity/gem5,briancoutinho0905/2dsampling,Weil0ng/gem5,Weil0ng/gem5,KuroeKurose/gem5,rjschof/gem5,HwisooSo/gemV-update,KuroeKurose/gem5,Weil0ng/gem5,gedare/gem5,rjschof/gem5,SanchayanMaity/gem5,Weil0ng/gem5,qizenguf/MLC-STT,Weil0ng/gem5,sobercoder/gem5,cancro7/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,cancro7/gem5,rallylee/gem5,gem5/gem5,aclifton/cpeg853-gem5,rallylee/gem5,KuroeKurose/gem5,gedare/gem5,briancoutinho0905/2dsampling,HwisooSo/gemV-update,TUD-OS/gem5-dtu,gem5/gem5,Weil0ng/gem5,sobercoder/gem5,aclifton/cpeg853-gem5,aclifton/cpeg853-gem5,rjschof/gem5,sobercoder/gem5,qizenguf/MLC-STT,powerjg/gem5-ci-test,rjschof/gem5,SanchayanMaity/gem5,TUD-OS/gem5-dtu,gedare/gem5,sobercoder/gem5,SanchayanMaity/gem5,HwisooSo/gemV-update,aclifton/cpeg853-gem5,gedare/gem5,powerjg/gem5-ci-test,TUD-OS/gem5-dtu,gem5/gem5,HwisooSo/gemV-update,powerjg/gem5-ci-test,rallylee/gem5,gem5/gem5,gem5/gem5,briancoutinho0905/2dsampling,qizenguf/MLC-STT,SanchayanMaity/gem5,sobercoder/gem5,powerjg/gem5-ci-test,powerjg/gem5-ci-test,TUD-OS/gem5-dtu,briancoutinho0905/2dsampling,briancoutinho0905/2dsampling,qizenguf/MLC-STT,powerjg/gem5-ci-test,sobercoder/gem5,powerjg/gem5-ci-test,rjschof/gem5,cancro7/gem5,briancoutinho0905/2dsampling,qizenguf/MLC-STT,briancoutinho0905/2dsampling,cancro7/gem5,aclifton/cpeg853-gem5,gem5/gem5,Weil0ng/gem5,rjschof/gem5,rallylee/gem5,sobercoder/gem5,gedare/gem5,SanchayanMaity/gem5,cancro7/gem5,rallylee/gem5,cancro7/gem5,gedare/gem5,HwisooSo/gemV-update,rallylee/gem5,KuroeKurose/gem5,KuroeKurose/gem5,cancro7/gem5,aclifton/cpeg853-gem5,gedare/gem5,HwisooSo/gemV-update,KuroeKurose/gem5,aclifton/cpeg853-gem5