Handle swift-sdk search paths

- Fixes a bug where includeSearchPaths and librarySearchPaths defined in
  a swift-sdk.json file were not properly respected. Updates
  UserToolchain to support these by converting them to extra flags.
  Ideally these flags would be handled with discrete properties instead
  of being bundled into extra flags.

Author: rauhul

Sources/PackageModel/UserToolchain.swift

@@ -482,6 +482,8 @@ public final class UserToolchain: Toolchain {
         }
 
         self.triple = triple
+
+        // Extract extra flags starting with flags from the destination's toolset
         self.extraFlags = BuildFlags(
             cCompilerFlags: destination.toolset.knownTools[.cCompiler]?.extraCLIOptions ?? [],
             cxxCompilerFlags: destination.toolset.knownTools[.cxxCompiler]?.extraCLIOptions ?? [],
@@ -492,6 +494,19 @@ public final class UserToolchain: Toolchain {
             linkerFlags: destination.toolset.knownTools[.linker]?.extraCLIOptions ?? [],
             xcbuildFlags: destination.toolset.knownTools[.xcbuild]?.extraCLIOptions ?? [])
 
+        // Extract the destination's include search paths into c, cxx, and swift
+        // compiler flags.
+        for path in destination.pathsConfiguration.includeSearchPaths ?? [] {
+            self.extraFlags.cCompilerFlags.append("-I\(path)")
+            self.extraFlags.cxxCompilerFlags.append("-I\(path)")
+            self.extraFlags.swiftCompilerFlags.append("-I\(path)")
+        }
+
+        // Extract the destination's library search paths into linker flags.
+        for path in destination.pathsConfiguration.librarySearchPaths ?? [] {
+            self.extraFlags.linkerFlags.append("-L\(path)")
+        }
+
         self.librarianPath = try UserToolchain.determineLibrarian(
             triple: triple,
             binDirectories: destination.toolset.rootPaths,

Tests/BuildTests/BuildPlanTests.swift

@@ -3547,13 +3547,15 @@ final class BuildPlanTests: XCTestCase {
             ],
             rootPaths: try UserToolchain.default.destination.toolset.rootPaths)
         let runtimeTriple = try Triple("armv7em-unknown-none-macho")
+        let sdkIncludeSearchPath = "/usr/lib/swift_static/none/include"
+        let sdkLibrarySearchPath = "/usr/lib/swift_static/none/lib"
         let destination = try Destination(
             runTimeTriple: runtimeTriple,
             properties: .init(
                 sdkRootPath: "/fake/sdk",
                 swiftStaticResourcesPath: "/usr/lib/swift_static/none",
-                includeSearchPaths: ["/usr/lib/swift_static/none"],
-                librarySearchPaths: ["/usr/lib/swift_static/none"],
+                includeSearchPaths: [sdkIncludeSearchPath],
+                librarySearchPaths: [sdkLibrarySearchPath],
                 toolsetPaths: []),
             toolset: toolSet,
             destinationDirectory: nil)
@@ -3596,7 +3598,9 @@ final class BuildPlanTests: XCTestCase {
         // Compile C Target
         let cLibCompileArguments = try result.target(for: "cLib").clangTarget().basicArguments(isCXX: false)
         let cLibCompileArgumentsPattern: [StringPattern] = [
-            jsonFlag(tool: .cCompiler), cliFlag(tool: .cCompiler),
+            jsonFlag(tool: .cCompiler),
+            .equal("-I\(sdkIncludeSearchPath)"),
+            cliFlag(tool: .cCompiler),
         ]
         XCTAssertMatch(cLibCompileArguments, cLibCompileArgumentsPattern)
         XCTAssertCount(0, cLibCompileArguments, jsonFlag(tool: .swiftCompiler))
@@ -3611,9 +3615,13 @@ final class BuildPlanTests: XCTestCase {
         // Compile Cxx Target
         let cxxLibCompileArguments = try result.target(for: "cxxLib").clangTarget().basicArguments(isCXX: true)
         let cxxLibCompileArgumentsPattern: [StringPattern] = [
-            jsonFlag(tool: .cCompiler), cliFlag(tool: .cCompiler),
+            jsonFlag(tool: .cCompiler),
+            .equal("-I\(sdkIncludeSearchPath)"),
+            cliFlag(tool: .cCompiler),
             .anySequence,
-            jsonFlag(tool: .cxxCompiler), cliFlag(tool: .cxxCompiler)
+            jsonFlag(tool: .cxxCompiler),
+            .equal("-I\(sdkIncludeSearchPath)"),
+            cliFlag(tool: .cxxCompiler)
         ]
         XCTAssertMatch(cxxLibCompileArguments, cxxLibCompileArgumentsPattern)
         XCTAssertCount(0, cxxLibCompileArguments, jsonFlag(tool: .swiftCompiler))
@@ -3628,13 +3636,19 @@ final class BuildPlanTests: XCTestCase {
         // Compile Swift Target
         let exeCompileArguments = try result.target(for: "exe").swiftTarget().compileArguments()
         let exeCompileArgumentsPattern: [StringPattern] = [
-            jsonFlag(tool: .swiftCompiler), cliFlag(tool: .swiftCompiler),
+            jsonFlag(tool: .swiftCompiler),
+            .equal("-I\(sdkIncludeSearchPath)"),
+            cliFlag(tool: .swiftCompiler),
             .anySequence,
-            "-Xcc", jsonFlag(tool: .cCompiler), "-Xcc", cliFlag(tool: .cCompiler),
+            "-Xcc", jsonFlag(tool: .cCompiler),
+            "-Xcc", .equal("-I\(sdkIncludeSearchPath)"),
+            "-Xcc", cliFlag(tool: .cCompiler),
             // TODO: Pass -Xcxx flags to swiftc (#6491)
             // Uncomment when downstream support arrives.
             // .anySequence,
-            // "-Xcxx", jsonFlag(tool: .cxxCompiler), "-Xcxx", cliFlag(tool: .cxxCompiler),
+            // "-Xcxx", jsonFlag(tool: .cxxCompiler),
+            // "-Xcc", .equal("-I\(sdkIncludeSearchPath)"),
+            // "-Xcxx", cliFlag(tool: .cxxCompiler),
         ]
         XCTAssertMatch(exeCompileArguments, exeCompileArgumentsPattern)
         XCTAssertCount(1, exeCompileArguments, jsonFlag(tool: .swiftCompiler))
@@ -3651,9 +3665,13 @@ final class BuildPlanTests: XCTestCase {
         // Link Product
         let exeLinkArguments = try result.buildProduct(for: "exe").linkArguments()
         let exeLinkArgumentsPattern: [StringPattern] = [
-            jsonFlag(tool: .swiftCompiler), cliFlag(tool: .swiftCompiler),
+            jsonFlag(tool: .swiftCompiler),
+            .equal("-I\(sdkIncludeSearchPath)"),
+            cliFlag(tool: .swiftCompiler),
             .anySequence,
-            "-Xlinker", jsonFlag(tool: .linker), "-Xlinker", cliFlag(tool: .linker),
+            "-Xlinker", jsonFlag(tool: .linker),
+            .equal("-L\(sdkLibrarySearchPath)"),
+            "-Xlinker", cliFlag(tool: .linker),
         ]
         XCTAssertMatch(exeLinkArguments, exeLinkArgumentsPattern)
         XCTAssertCount(1, exeLinkArguments, jsonFlag(tool: .swiftCompiler))