:bug: Fix invalid shellAppDir on OS X
:bug: Fix invalid shellAppDir on OS X

This resolves the "perfect storm" scenario that resulted when #8829
got merged with `master`. The merge resulted in an invalid shellAppDir
being used, which in turn propagated all the way into script/set-version
and thus the plist update commands failed since it was pointed at a path
which did not exist.

TL;DR: the .app suffix was missing from shellAppDir due to code reordering.

/cc @maxbrunsfeld

gzzhanghao/atom,AdrianVovk/substance-ide,G-Baby/atom,AdrianVovk/substance-ide,kandros/atom,helber/atom,nucked/atom,scippio/atom,Austen-G/BlockBuilder,cyzn/atom,sotayamashita/atom,ivoadf/atom,ivoadf/atom,Klozz/atom,seedtigo/atom,DiogoXRP/atom,brettle/atom,johnrizzo1/atom,alfredxing/atom,gontadu/atom,PKRoma/atom,Arcanemagus/atom,liuderchi/atom,ivoadf/atom,FIT-CSE2410-A-Bombs/atom,transcranial/atom,chfritz/atom,originye/atom,liuderchi/atom,niklabh/atom,alfredxing/atom,nucked/atom,rlugojr/atom,bj7/atom,atom/atom,efatsi/atom,ykeisuke/atom,florianb/atom,helber/atom,mrodalgaard/atom,hellendag/atom,pkdevbox/atom,mrodalgaard/atom,ashneo76/atom,kaicataldo/atom,tjkr/atom,transcranial/atom,tanin47/atom,fscherwi/atom,bsmr-x-script/atom,ykeisuke/atom,sotayamashita/atom,seedtigo/atom,Mokolea/atom,Klozz/atom,tjkr/atom,cyzn/atom,stinsonga/atom,CraZySacX/atom,jordanbtucker/atom,bj7/atom,scippio/atom,svanharmelen/atom,RuiDGoncalves/atom,001szymon/atom,seedtigo/atom,Locke23rus/atom,florianb/atom,G-Baby/atom,xream/atom,ykeisuke/atom,medovob/atom,chfritz/atom,gontadu/atom,kevinrenaers/atom,tjkr/atom,Huaraz2/atom,Ingramz/atom,mdumrauf/atom,bolinfest/atom,lpommers/atom,stinsonga/atom,PKRoma/atom,florianb/atom,kevinrenaers/atom,bolinfest/atom,svanharmelen/atom,originye/atom,t9md/atom,efatsi/atom,Austen-G/BlockBuilder,daxlab/atom,originye/atom,gzzhanghao/atom,efatsi/atom,yamhon/atom,brettle/atom,svanharmelen/atom,alfredxing/atom,alexandergmann/atom,atom/atom,tanin47/atom,gzzhanghao/atom,lpommers/atom,hellendag/atom,wiggzz/atom,rlugojr/atom,brumm/atom,florianb/atom,decaffeinate-examples/atom,me-benni/atom,mdumrauf/atom,kevinrenaers/atom,t9md/atom,dijs/atom,ObviouslyGreen/atom,FIT-CSE2410-A-Bombs/atom,ObviouslyGreen/atom,Ingramz/atom,Arcanemagus/atom,me-benni/atom,ashneo76/atom,fscherwi/atom,alexandergmann/atom,daxlab/atom,hellendag/atom,medovob/atom,DiogoXRP/atom,niklabh/atom,jordanbtucker/atom,kaicataldo/atom,andrewleverette/atom,decaffeinate-examples/atom,Mokolea/atom,johnrizzo1/atom,beni55/atom,rookie125/atom,pengshp/atom,nucked/atom,beni55/atom,Huaraz2/atom,DiogoXRP/atom,xream/atom,Klozz/atom,PKRoma/atom,G-Baby/atom,andrewleverette/atom,niklabh/atom,jeremyramin/atom,florianb/atom,CraZySacX/atom,kandros/atom,pkdevbox/atom,yamhon/atom,Austen-G/BlockBuilder,dijs/atom,001szymon/atom,tanin47/atom,ObviouslyGreen/atom,AlexxNica/atom,ardeshirj/atom,liuderchi/atom,AlexxNica/atom,bolinfest/atom,transcranial/atom,johnhaley81/atom,ardeshirj/atom,stinsonga/atom,kaicataldo/atom,johnhaley81/atom,andrewleverette/atom,Mokolea/atom,chfritz/atom,beni55/atom,CraZySacX/atom,decaffeinate-examples/atom,wiggzz/atom,bj7/atom,kandros/atom,AlexxNica/atom,t9md/atom,daxlab/atom,RuiDGoncalves/atom,rookie125/atom,dijs/atom,stinsonga/atom,001szymon/atom,jordanbtucker/atom,wiggzz/atom,jeremyramin/atom,mdumrauf/atom,brettle/atom,sotayamashita/atom,xream/atom,gontadu/atom,johnrizzo1/atom,ashneo76/atom,johnhaley81/atom,Ingramz/atom,scippio/atom,bsmr-x-script/atom,Locke23rus/atom,yamhon/atom,atom/atom,Arcanemagus/atom,ardeshirj/atom,rlugojr/atom,mrodalgaard/atom,fscherwi/atom,decaffeinate-examples/atom,brumm/atom,brumm/atom,pengshp/atom,bsmr-x-script/atom,rookie125/atom,Austen-G/BlockBuilder,Austen-G/BlockBuilder,FIT-CSE2410-A-Bombs/atom,cyzn/atom,alexandergmann/atom,jeremyramin/atom,Huaraz2/atom,pkdevbox/atom,liuderchi/atom,Locke23rus/atom,pengshp/atom,RuiDGoncalves/atom,lpommers/atom,medovob/atom,me-benni/atom,Austen-G/BlockBuilder,AdrianVovk/substance-ide,helber/atom