WIP: Add Linux support

Author: abertelrud

Sources/Build/BuildPlan.swift

@@ -504,8 +504,7 @@ public final class SwiftTargetBuildDescription {
 
     /// The path to the swiftmodule file after compilation.
     var moduleOutputPath: AbsolutePath {
-        let dirPath = (target.type == .executable) ? tempsPath : buildParameters.buildPath
-        return dirPath.appending(component: target.c99name + ".swiftmodule")
+        return buildParameters.buildPath.appending(component: target.c99name + ".swiftmodule")
     }
 
     /// The path to the wrapped swift module which is created using the modulewrap tool. This is required

Sources/Build/ManifestBuilder.swift

@@ -632,15 +632,25 @@ extension LLBuildManifestBuilder {
     private func addMainSymbolRemovalCmd(toolchain: Toolchain,
                                          inputFile: AbsolutePath, outputFile: AbsolutePath,
                                          mainSymbolListFile: AbsolutePath) {
-        let args = [
-            // FIXME: Using `nmedit` only works on Darwin.  For Linux (and Windows?) we need to use `strip` from the
-            //        `binutils`, and for other platforms, who knows.  This needs to be made generic.
-            // FIXME: Even on Darwin, we need the toolchain to provide the path of the `nmedit` tool.
-            toolchain.swiftCompiler.parentDirectory.appending(component: "nmedit").pathString,
-            "-R", mainSymbolListFile.pathString,
-            inputFile.pathString,
-            "-o", outputFile.pathString
-        ]
+        let args: [String]
+        #if canImport(Darwin)
+            // On Darwin systems, use `nmedit` to remove the `main` symbol.
+            args = [
+                // FIXME: The toolchain should provide the path of the `nmedit` tool.
+                toolchain.swiftCompiler.parentDirectory.appending(component: "nmedit").pathString,
+                "-R", mainSymbolListFile.pathString,
+                inputFile.pathString,
+                "-o", outputFile.pathString
+            ]
+        #else
+            // On non-Darwin systems, use `objcopy` from `binutils` to mark the `main` symbol as local.
+            args = [
+                "objcopy",
+                "-L", "main",
+                inputFile.pathString,
+                outputFile.pathString
+            ]
+        #endif
         manifest.addShellCmd(
             name: outputFile.pathString,
             description: "Eliding symbols from \(outputFile.basename)",