tests: remove ld-add_ast_path feature

We don't support building Swift with linkers that don't support this feature.

Swift SVN r27180

Author: gribozavr

test/DebugInfo/ASTSection.swift

@@ -15,8 +15,6 @@
 
 // UNSUPPORTED: OS=linux-gnu
 
-// REQUIRES: ld-add_ast_path
-
 // Test ASTSection_linker.swift builds this code 
 // with separate compile and link steps.
 

test/DebugInfo/ASTSection_linker.swift

@@ -15,7 +15,6 @@
 // RUN: %lldb-moduleimport-test %t/ASTSection.dylib | FileCheck %s
 
 // REQUIRES: OS=macosx
-// REQUIRES: ld-add_ast_path
 
 // CHECK: Loaded module ASTSection from
 // CHECK: - Target: {{.+}}-{{.+}}-{{.+}}

test/Driver/sdk-link.swift

@@ -4,9 +4,7 @@
 // RUN: %target-build-swift -g -o %t/sdk-link %s
 // RUN: %target-run %t/sdk-link | FileCheck %s
 
-// XFAIL: linux
-
-// REQUIRES: ld-add_ast_path
+// REQUIRES: objc_interop
 
 import Foundation
 

test/Driver/temp-files.swift

@@ -1,4 +1,5 @@
-// REQUIRES: ld-add_ast_path
+// REQUIRES: objc_interop
+// FIXME: actually, this test requires Mach-O.
 
 // RUN: rm -rf %t && mkdir -p %t/tmp/ && touch %t/tmp/dummy
 // RUN: env TMPDIR=%t/tmp/ %target-swiftc_driver -emit-executable %s -o %t/main