CMake build broken in CI on Windows

``` [145/240] Generate runner for test target HyloTests FAILED: [code=255] HyloTests-test_main/main.swift D:/a/hylo/hylo/hylo/.cmake-build/HyloTests-test_main/main.swift Tests\CMakeFiles\main.swift-0b702ca.bat d805af0bce0c2d34 (set was unexpected at this time. [146/240] Generate Swift test file 1 for LibraryTests/TestCases ``` Seems like a syntax error in some generated bat file.