[build] Include unit test logs in make package-test-errors

The `xa-test-errors*.zip` files generated by
`make package-test-errors` only included "failing" *MSBuild* unit test
projects [^1].  This means that if there were unit test failures that
*didn't* have a corresponding MSBuild unit test, the only output that
*might* be useful were the `.binlog` files in in
`xa-build-status*.zip`.

Not all useful unit test output will be in the `.binlog` files.

Update `make package-test-errors` so that the `xa-test-errors*.zip`
file *also* contains the `TestResult-*.xml` NUnit output files and the
`bin/Test*/TestOutput-*.txt` files produced by NUnit test execution.
This allows observing e.g. `Console.WriteLine()` messages generated
when executing the unit tests.

[^1]: The *intent* for `make package-test-errors` was that it would
      only produce file if there actually were failures, which is why
      the target rules were conditional on `bin/Test*/temp` existing,
      because that held the unit test-generated MSBuild projects.

      However, that's *also* where the unit test-generated MSBuild
      *NuGet packages* resided, in e.g. `bin/TestDebug/temp/packages`.
      Nothing deletes the `packages` directory.  Consequently,
      `make package-test-errors` *always* generated an
      `xa-test-errors*.zip` file, even when all tests passed!

Author: jonpryor

build-tools/scripts/Packaging.mk

@@ -66,10 +66,8 @@ package-deb: $(ZIP_OUTPUT)
 _TEST_ERRORS_BASENAME   = xa-test-errors-v$(PRODUCT_VERSION).$(-num-commits-since-version-change)_$(OS_NAME)-$(OS_ARCH)_$(GIT_BRANCH)_$(GIT_COMMIT)
 
 "$(_TEST_ERRORS_BASENAME).zip" package-test-errors:
-ifneq ($(wildcard bin/Test*/temp),)
-	build-tools/scripts/ln-to.sh -r . -o "$(_TEST_ERRORS_BASENAME)" bin/Test*/temp
+	build-tools/scripts/ln-to.sh -r . -o "$(_TEST_ERRORS_BASENAME)" bin/Test*/temp TestResult-*.xml bin/Test*/TestOutput-*.txt
 	zip -r "$(_TEST_ERRORS_BASENAME).zip" "$(_TEST_ERRORS_BASENAME)"
-endif # We have test error output
 
 _BUILD_STATUS_BUNDLE_INCLUDE = \
 	Configuration.OperatingSystem.props \