compilation error using xcode-12.4

When compiling taskwarrior-reminders I get the following error using xcode 12.4(12D4e):
```
make install
swift package clean
rm -rf .build
swift build -Xlinker -sectcreate -Xlinker __TEXT -Xlinker __info_plist -Xlinker Info.plist --configuration release
Fetching https://github.com/eonil/FSEvents
Fetching https://github.com/SwiftyJSON/SwiftyJSON
Cloning https://github.com/eonil/FSEvents
Resolving https://github.com/eonil/FSEvents at 0.1.6
Cloning https://github.com/SwiftyJSON/SwiftyJSON
Resolving https://github.com/SwiftyJSON/SwiftyJSON at 5.0.0
/Users/erik/Projects/taskwarrior-reminders/Sources/Repositories/Taskwarrior.swift:29:9: warning: result of call to 'execTaskwarrior(args:input:)' is unused
execTaskwarrior(args: ["sync"])
^ ~~~~~~~~~~~~~~~~
/Users/erik/Projects/taskwarrior-reminders/Sources/Repositories/Taskwarrior.swift:47:9: warning: result of call to 'execTaskwarrior(args:input:)' is unused
execTaskwarrior(args: ["reminderID:" + t.reminderID!, "-COMPLETED", "delete"])
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/erik/Projects/taskwarrior-reminders/Sources/Repositories/Taskwarrior.swift:88:9: warning: result of call to 'execTaskwarrior(args:input:)' is unused
execTaskwarrior(args: args, input: task)
^ ~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/erik/Projects/taskwarrior-reminders/Sources/Repositories/Taskwarrior.swift:112:17: warning: initialization of immutable value 'jsonEncoder' was never used; consider replacing with assignment to '_' or removing it
let jsonEncoder = JSONEncoder.init()
~~~~^~~~~~~~~~~
_
/Users/erik/Projects/taskwarrior-reminders/Sources/Repositories/Taskwarrior.swift:132:9: warning: no calls to throwing functions occur within 'try' expression
try process.launch()
^
/Users/erik/Projects/taskwarrior-reminders/Sources/Sync/main.swift:16:9: warning: initialization of immutable value 'fsobserver' was never used; consider replacing with assignment to '_' or removing it
let fsobserver = TaskwarriorObserver(reminders, syncSince: syncStart, lock: lock)
~~~~^~~~~~~~~~
_
/Users/erik/Projects/taskwarrior-reminders/Sources/Sync/RemindersObserver.swift:43:25: warning: initialization of immutable value 'syncResult' was never used; consider replacing with assignment to '_' or removing it
let syncResult = self.tw.upsertToTaskwarrior(
~~~~^~~~~~~~~~
_
/Users/erik/Projects/taskwarrior-reminders/Sources/Sync/TaskwarriorObserver.swift:33:25: warning: result of call to 'upsertToTaskwarrior' is unused
self.tw.upsertToTaskwarrior(syncResult.task)
^ ~~~~~~~~~~~~~~~~~
[8/8] Linking task-reminders-sync
rm -f /usr/local/bin/task-reminders-sync
launchctl remove com.blampe.task-reminders-sync || true
cp .build/release/task-reminders-sync task-reminders-sync
ln -Fs /Users/erik/Projects/taskwarrior-reminders/task-reminders-sync /usr/local/bin/task-reminders-sync
cp com.blampe.task-reminders-sync.plist ~/Library/LaunchAgents/.
cp: /Users/erik/Library/LaunchAgents/.: No such file or directory
make: *** [install] Error 1
```

Start with the final `cp` failure in the `make install` output and inspect the install target's commands around `~/Library/LaunchAgents` and `com.blampe.task-reminders-sync.plist`. Re-run the install flow and verify that the launch agent files are copied successfully without the reported directory error.

Written by the indexing model from the issue text.