[ELF] Don't pass ELF shared objects to autolink-extract

This is a version of swiftlang/swift#30465 for the new driver.

Since shared objects are classified as `.object`, they end up getting
passed to the autolink-extract job.

For ELF platforms, this is unnecessary, since the autolink entries are
not in the final shared object, so the autolink-extract process will not
find any entries.

Additionally, in ELF platforms, `.so` files can actually be linker
scripts (text files) with instructions for the actual linker, which the
autolink-extract job will not understand and will fail.

For those two reasons, modify the autolink-extract inputs to skip over
objects in ELF platforms that have the `.so` extension.

Author: drodriguez

Sources/SwiftDriver/Jobs/Planning.swift

@@ -599,7 +599,13 @@ extension Driver {
     addJob: (Job) -> Void)
   throws
   {
-    let autolinkInputs = linkerInputs.filter { $0.type == .object }
+    let autolinkInputs = linkerInputs.filter { input in
+      // Shared objects on ELF platforms don't have a swift1_autolink_entries
+      // section in them because the section in the .o files is marked as
+      // SHF_EXCLUDE. They can also be linker scripts which swift-autolink-extract
+      // does not handle.
+      return input.type == .object && !(targetTriple.objectFormat == .elf && input.file.`extension` == "so")
+    }
     if let autolinkExtractJob = try autolinkExtractJob(inputs: autolinkInputs) {
       addJob(autolinkExtractJob)
       autolinkExtractJob.outputs.forEach(addLinkerInput)

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -2038,6 +2038,34 @@ final class SwiftDriverTests: XCTestCase {
       XCTAssertFalse(cmd.contains(.flag("-static")))
     }
 
+    do {
+      // Linux shared objects (.so) are not offered to autolink-extract
+      try withTemporaryDirectory { path in
+        try localFileSystem.writeFileContents(
+          path.appending(components: "libEmpty.so")) { $0 <<< "/* empty */" }
+
+        var driver = try Driver(args: commonArgs + ["-emit-executable", "-target", "x86_64-unknown-linux", "libEmpty.so"], env: env)
+        let plannedJobs = try driver.planBuild()
+
+        XCTAssertEqual(plannedJobs.count, 4)
+
+        let autolinkExtractJob = plannedJobs[2]
+        XCTAssertEqual(autolinkExtractJob.kind,.autolinkExtract)
+
+        let autolinkCmd = autolinkExtractJob.commandLine
+        XCTAssertTrue(commandContainsTemporaryPath(autolinkCmd, "foo.o"))
+        XCTAssertTrue(commandContainsTemporaryPath(autolinkCmd, "bar.o"))
+        XCTAssertTrue(commandContainsTemporaryPath(autolinkCmd, "Test.autolink"))
+        XCTAssertFalse(
+          autolinkCmd.contains {
+            guard case .path(let path) = $0 else { return false }
+            if case .relative(let p) = path, p.basename == "libEmpty.so" { return true }
+            return false
+          }
+        )
+      }
+    }
+
     do {
       // static linux linking
       var driver = try Driver(args: commonArgs + ["-emit-library", "-static", "-target", "x86_64-unknown-linux"], env: env)