ObjectiveC: Respect OSX_ARCHITECTURES for OBJC

Fix a typo from commit 940fc629 (macOS: Respect OSX_ARCHITECTURES for
ASM, 2020-08-21, v3.19.0-rc1~270^2).

Fixes: #22152
34 jobs for !6090 with objc-osx-architectures in 14 minutes and 10 seconds (queued for 3 seconds)
latest detached
Status Name Job ID Coverage
  Build
manual build:centos6-x86_64 #5764642
build docker linux cmake manual
passed build:debian10-iwyu #5764639
cmake build docker linux

00:01:29

manual build:fedora33-ninja #5764643
cmake build docker linux linux-3.17 manual
passed build:fedora33-sphinx #5764641
cmake build docker linux linux-3.17

00:02:38

passed build:fedora33-tidy #5764640
cmake build docker linux linux-3.17

00:03:55

passed build:macos-x86_64-makefiles #5764645
cmake macos shell xcode-12.4 nonconcurrent manual

00:02:42

manual build:macos-x86_64-ninja #5764644
cmake macos shell xcode-12.4 nonconcurrent manual
manual build:windows-vs2019-x64-ninja #5764646
cmake windows shell vs2019 msvc-19.28-16.9 nonconcurrent manual
 
  Test
created test:fedora33-ninja #5764647
cmake docker linux linux-3.17 x11
passed test:macos-x86_64-makefiles #5764649
cmake macos shell xcode-12.4 nonconcurrent

00:11:00

created test:macos-x86_64-ninja #5764648
cmake macos shell xcode-12.4 nonconcurrent
created test:windows-vs2019-x64-ninja #5764650
cmake windows shell vs2019 msvc-19.28-16.9 nonconcurrent
 
  Test Ext
created test:cuda10.2-nvidia #5764653
cmake cuda-rt docker linux
created test:debian10-ninja #5764651
cmake build docker linux linux-3.17
created test:fedora33-makefiles #5764652
cmake build docker linux linux-3.17
created test:fedora33-ninja-multi #5764654
cmake build docker linux linux-3.17
created test:macos-x86_64-xcode #5764655
cmake macos shell xcode-12.4 concurrent
created test:windows-vs2019-x64 #5764656
cmake windows shell vs2019 msvc-19.28-16.9 concurrent
 
  External
passed cdash

passed ghostflow-check-master

passed ghostflow-check-release

passed ghostflow-stager

passed cdash

passed cdash

passed cdash

passed cdash

passed cdash

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager