Splat build.ps1 arguments as a hashtable so the dispatch inputs work

The workflow_dispatch inputs have no effect except to break the run. Array
splatting binds positionally, and build.ps1 declares only switches with no
positional parameters, so any non-default input fails the build immediately:

  build.ps1: A positional parameter cannot be found that accepts argument
  '-SkipCoverage'.

Only the all-defaults path works today, because that leaves the array empty.
Splatting a hashtable binds by parameter name instead.

This is invisible on push and pull_request, which never populate the inputs,
so it only bites someone dispatching the workflow by hand -- which is also the
only way to get a matrix run on a branch with no pull request open.

Author: darkfader

.github/workflows/ci.yml

@@ -81,11 +81,14 @@ jobs:
         PACK_NUGETS: ${{ github.event_name != 'workflow_dispatch' || inputs.pack_nugets || inputs.publish_nuget }}
         CREATE_ARCHIVE: ${{ github.event_name != 'workflow_dispatch' || inputs.upload_artifacts }}
       run: |
-        $buildArguments = @()
-        if ($env:RUN_TESTS -ne 'true') { $buildArguments += '-SkipTests' }
-        if ($env:COLLECT_COVERAGE -ne 'true') { $buildArguments += '-SkipCoverage' }
-        if ($env:PACK_NUGETS -ne 'true') { $buildArguments += '-SkipPack' }
-        if ($env:CREATE_ARCHIVE -ne 'true') { $buildArguments += '-SkipArchive' }
+        # Splat a hashtable, not an array. Array splatting binds positionally, and
+        # build.ps1 declares only switches, so any non-empty array fails with
+        # "A positional parameter cannot be found that accepts argument '-SkipTests'".
+        $buildArguments = @{}
+        if ($env:RUN_TESTS -ne 'true') { $buildArguments['SkipTests'] = $true }
+        if ($env:COLLECT_COVERAGE -ne 'true') { $buildArguments['SkipCoverage'] = $true }
+        if ($env:PACK_NUGETS -ne 'true') { $buildArguments['SkipPack'] = $true }
+        if ($env:CREATE_ARCHIVE -ne 'true') { $buildArguments['SkipArchive'] = $true }
         ./Build/build.ps1 @buildArguments
 
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