Swift target doesn't run tests on OSX M1 mac

From a test dir generated by test rig:

```
beast:/private/var/folders/w1/_nr4stn13lq0rvjdkwh7q8cc0000gn/T/SwiftRunner-main-1668879163413 $ swift build -c release -Xswiftc -I/Users/parrt/antlr/code/antlr4/runtime/Swift/.build/release -Xlinker -L/Users/parrt/antlr/code/antlr4/runtime/Swift/.build/release -Xlinker -lAntlr4 -Xlinker -rpath -Xlinker /Users/parrt/antlr/code/antlr4/runtime/Swift/.build/release
Building for production...
/private/var/folders/w1/_nr4stn13lq0rvjdkwh7q8cc0000gn/T/SwiftRunner-main-1668879163413/main.swift:1:8: error: no such module 'Antlr4'
import Antlr4
^
```

Just running a build from runtime dir works:

```
beast:compare-ATN-sim-output:~/antlr/code/antlr4/runtime/Swift $ swift build
'antlr4': warning: Invalid Exclude '/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/runtime/Swift/Tests/Threading.g4': File not found.
'antlr4': warning: Invalid Exclude '/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/runtime/Swift/Tests/VisitorBasic.g4': File not found.
'antlr4': warning: Invalid Exclude '/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/runtime/Swift/Tests/VisitorCalc.g4': File not found.
'antlr4': warning: Invalid Exclude '/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/runtime/Swift/Tests/LexerB.g4': File not found.
'antlr4': warning: Invalid Exclude '/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/runtime/Swift/Tests/LexerA.g4': File not found.
'antlr4': warning: found 21 file(s) which are unhandled; explicitly declare them as resources or exclude from the target
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/LexerA.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorCalc.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/LexerA.g4
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/Threading.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorBasicLexer.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/Threading.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/Threading.g4
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/LexerA.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/LexerB.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/VisitorBasic.g4
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorCalcLexer.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorCalc.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/LexerB.g4
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/VisitorCalc.g4
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/LexerB.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorBasic.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorBasicLexer.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/ThreadingLexer.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/ThreadingLexer.tokens
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorCalcLexer.interp
/Users/parrt/antlr/code/antlr4/runtime/Swift/Tests/Antlr4Tests/gen/VisitorBasic.tokens

Building for debugging...
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: warning: switch covers known cases, but 'Stream.Status' may have additional unknown values, possibly added in future versions
switch stream.streamStatus {
^
/Users/parrt/antlr/code/antlr4/runtime/Swift/Sources/Antlr4/UnbufferedCharStream.swift:336:9: note: handle unknown values using "@unknown default"
switch stream.streamStatus {
^
[156/156] Archiving libAntlr4Static.a
Build complete! (4.32s)
```

Reproduce the failure from the generated test directory using the shown swift build command, then compare it with a build from runtime/Swift. Inspect the generated main.swift invocation and the Swift runtime package layout; done means the generated Swift target can import Antlr4 and run its tests on an OSX M1 Mac.

Written by the indexing model from the issue text.