Disable explicit module builds for the index arena

Explicit module arguments are removed for the arguments returned for
indexing. Also disable them for preparation in general so we're not
mixing between the two.

Resolves rdar://147354913.

Author: bnbarham

Sources/SWBCore/Settings/Settings.swift

@@ -3815,6 +3815,11 @@ private class SettingsBuilder {
             table.push(BuiltinMacros.EFFECTIVE_PLATFORM_NAME, literal: MacCatalystInfo.publicSDKBuiltProductsDirSuffix)
         }
 
+        table.push(BuiltinMacros.SWIFT_ENABLE_EXPLICIT_MODULES, literal: .disabled)
+        table.push(BuiltinMacros._EXPERIMENTAL_SWIFT_EXPLICIT_MODULES, literal: .disabled)
+        table.push(BuiltinMacros.CLANG_ENABLE_EXPLICIT_MODULES, literal: false)
+        table.push(BuiltinMacros._EXPERIMENTAL_CLANG_EXPLICIT_MODULES, literal: false)
+
         push(table, .exported)
     }
 

Tests/SWBTaskConstructionTests/IndexBuildTaskConstructionTests.swift

@@ -546,6 +546,10 @@ fileprivate struct IndexBuildTaskConstructionTests: CoreBasedTests {
             try results.checkTask(.matchTargetName("AppTarget"), .matchRuleItem("SwiftDriver Compilation Requirements")) { task in
                 task.checkRuleInfo(["SwiftDriver Compilation Requirements", "AppTarget", "normal", "x86_64", "com.apple.xcode.tools.swift.compiler"])
 
+                // Explicit modules are disabled for semantic functionality currently, make sure it is also disabled
+                // for preparation in general.
+                task.checkCommandLineDoesNotContain("-explicit-module-build")
+
                 let skipFlag = swiftFeatures.has(.experimentalSkipAllFunctionBodies) ? "-experimental-skip-all-function-bodies" : "-experimental-skip-non-inlinable-function-bodies"
                 task.checkCommandLineContains(["-module-name", "AppTarget", "-Onone", "-Xfrontend", skipFlag, "-emit-dependencies", "-emit-module", "-emit-module-path", "-emit-objc-header", "-emit-objc-header-path"])
                 if swiftFeatures.has(.experimentalAllowModuleWithCompilerErrors) {
@@ -793,8 +797,11 @@ fileprivate struct IndexBuildTaskConstructionTests: CoreBasedTests {
 
             results.checkNoTask(.matchCommandLineArgument("clang-stat-cache"))
 
-            try results.checkTask(.matchTargetName("AppTarget"), .matchRuleItem("CompileC")) { task in
+            // Explicit modules are disabled for semantic functionality currently, make sure it is also disabled
+            // for preparation in general.
+            results.checkNoTask(.matchRuleItem("ScanDependencies"))
 
+            try results.checkTask(.matchTargetName("AppTarget"), .matchRuleItem("CompileC")) { task in
                 if clangFeatures.has(.allowPcmWithCompilerErrors) {
                     task.checkCommandLineContains(["-Xclang", "-fallow-pcm-with-compiler-errors"])
                 } else {