check linker settings by triples' object format instead of os name

Author: michael-yuji

Sources/Build/BuildDescription/ProductBuildDescription.swift

@@ -270,11 +270,14 @@ public final class ProductBuildDescription: SPMBuildCore.ProductBuildDescription
         // Set rpath such that dynamic libraries are looked up
         // adjacent to the product, unless overridden.
         if !self.buildParameters.linkingParameters.shouldDisableLocalRpath {
-            if triple.isLinux() || triple.isFreeBSD() {
+            switch triple.objectFormat {
+            case .elf:
                 args += ["-Xlinker", "-rpath=$ORIGIN"]
-            } else if triple.isDarwin() {
+            case .macho:
                 let rpath = self.product.type == .test ? "@loader_path/../../../" : "@loader_path"
                 args += ["-Xlinker", "-rpath", "-Xlinker", rpath]
+            case .coff, .xcoff, .wasm:
+                break
             }
         }
         args += ["@\(self.linkFileListPath.pathString)"]

Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift

@@ -144,7 +144,7 @@ public final class SwiftModuleBuildDescription {
     public var moduleOutputPath: AbsolutePath { // note: needs to be public because of sourcekit-lsp
         // If we're an executable and we're not allowing test targets to link against us, we hide the module.
         let triple = buildParameters.triple
-        let allowLinkingAgainstExecutables = (triple.isDarwin() || triple.isLinux() || triple.isFreeBSD() || triple.isWindows()) && self.toolsVersion >= .v5_5
+        let allowLinkingAgainstExecutables = [.coff, .macho, .elf].contains(triple.objectFormat) && self.toolsVersion >= .v5_5
         let dirPath = (target.type == .executable && !allowLinkingAgainstExecutables) ? self.tempsPath : self.modulesPath
         return dirPath.appending(component: "\(self.target.c99name).swiftmodule")
     }

Sources/Build/BuildPlan/BuildPlan.swift

@@ -146,11 +146,12 @@ extension BuildParameters {
     /// platform, or nil if the linker doesn't support it for the platform.
     func linkerFlagsForRenamingMainFunction(of target: ResolvedModule) -> [String]? {
         let args: [String]
-        if self.triple.isApple() {
+        switch self.triple.objectFormat {
+        case .macho:
             args = ["-alias", "_\(target.c99name)_main", "_main"]
-        } else if self.triple.isLinux() || self.triple.isFreeBSD() {
+        case .elf:
             args = ["--defsym", "main=\(target.c99name)_main"]
-        } else {
+        case .xcoff, .coff, .wasm:
             return nil
         }
         return args.asSwiftcLinkerFlags()