tests crash on windows

[compnerd]

Test Case 'CachingBuildTests.testCacheBuildEndToEndBuild' started at 2023-12-14 16:42:43.920
C:\Users\abdulras\AppData\Local\Programs\Swift\Toolchains\0.0.0+Asserts\usr\bin\swift-frontend.exe -frontend -scan-dependencies -target x86_64-unknown-windows-msvc -disable-objc-interop -sdk C:\Users\abdulras\AppData\Local\Programs\Swift\Platforms\0.0.0\Windows.platform\Developer\SDKs\Windows.sdk -I S:\\SourceCache\\apple\\swift-driver\\TestInputs\\ExplicitModuleBuilds\\CHeaders -I S:\\SourceCache\\apple\\swift-driver\\TestInputs\\ExplicitModuleBuilds\\Swift -module-cache-path C:\\Users\\abdulras\\AppData\\Local\\Temp\\TemporaryDirectory.wrsjbq\\ModuleCache -empty-abi-descriptor -resource-dir C:\Users\abdulras\AppData\Local\Programs\Swift\Toolchains\0.0.0+Asserts\usr\lib\swift -cache-compile-job -cas-path C:\\Users\\abdulras\\AppData\\Local\\Temp\\TemporaryDirectory.wrsjbq\\cas -Rcache-compile-job -module-name testCachingBuild -plugin-path S:\SourceCache\apple\swift-driver\.build\bin -plugin-path S:\SourceCache\apple\swift-driver\.build\local\bin C:\\Users\\abdulras\\AppData\\Local\\Temp\\TemporaryDirectory.wrsjbq\\testCachingBuild.swift
<EXPR>:0: error: CachingBuildTests.testCacheBuildEndToEndBuild : threw error "libSwiftScan CAS error: OnDiskCache is disabled"
Test Case 'CachingBuildTests.testCacheBuildEndToEndBuild' failed (0.097 seconds)
Test Case 'CachingBuildTests.testCacheBuildEndToEndWithBinaryHeaderDeps' started at 2023-12-14 16:42:44.017
warning: Could not read SDKSettings.json for SDK at: C:\Users\abdulras\AppData\Local\Programs\Swift\Platforms\0.0.0\Windows.platform\Developer\SDKs\Windows.sdk
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
SwiftDriverTests/CachingBuildTests.swift:678: Fatal error: 'try!' expression unexpectedly raised an error: libSwiftScan dependency scan query failed
Current stack trace:
0    (null)                             0x00007ffd952ee9a0 swift_stdlib_reportFatalErrorInFile + 132

[cachemeifyoucan]

This is a regression from my change af31831

I try to simply the logic by guard the tests behind a feature flag but unfortunately feature flag can't have different value for windows. Need to add back the check for scanner support.