Trying to build without CMake installed gives a confusing error message

[carlosmn]

Namely

.\build.libgit2.ps1 14
Index was outside the bounds of the array.
At C:\source\github.com\libgit2sharp\libgit2sharp.nativebinaries\build.libgit2.ps1:71 char:16
+     $cmake = @(Get-Command cmake.exe)[0] 2>$null
+                ~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [], IndexOutOfRangeException
    + FullyQualifiedErrorId : System.IndexOutOfRangeException

which seems to come from @(Get-Command cmake.exe) returning an empty array.