[Linux] Reorder the -Xlinker and -l arguments

- Move the -Xlinker and -l options to just before swift_end.o

- Add testcase to check linker option ordering.

Author: spevans

lib/Driver/ToolChains.cpp

@@ -1534,8 +1534,6 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
   addPrimaryInputsOfType(Arguments, context.Inputs, types::TY_Object);
   addInputsOfType(Arguments, context.InputActions, types::TY_Object);
 
-  context.Args.AddAllArgs(Arguments, options::OPT_Xlinker);
-  context.Args.AddAllArgs(Arguments, options::OPT_linker_option_Group);
   for (const Arg *arg : context.Args.filtered(options::OPT_F,
                                               options::OPT_Fsystem)) {
     if (arg->getOption().matches(options::OPT_Fsystem))
@@ -1609,6 +1607,9 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
         Twine("-u", llvm::getInstrProfRuntimeHookVarName())));
   }
 
+  context.Args.AddAllArgs(Arguments, options::OPT_Xlinker);
+  context.Args.AddAllArgs(Arguments, options::OPT_linker_option_Group);
+
   // Just before the output option, allow GenericUnix toolchains to add
   // additional inputs.
   auto PostInputObjectPath = getPostInputObjectPath(ObjectLibPath);

test/Driver/linker-args-order-linux.swift

@@ -0,0 +1,11 @@
+// Statically link a "hello world" program
+// REQUIRES: OS=linux-gnu
+// REQUIRES: static_stdlib
+print("hello world!")
+// RUN: %empty-directory(%t)
+// RUN: %target-swiftc_driver -v -static-stdlib -o %t/static-stdlib %s -Xlinker --no-allow-multiple-definition 2>&1| %FileCheck %s
+// CHECK: Swift version
+// CHECK: Target: x86_64-unknown-linux-gnu
+// CHECK: {{.*}}/swift -frontend -c -primary-file {{.*}}/linker-args-order-linux.swift -target x86_64-unknown-linux-gnu -disable-objc-interop
+// CHECK: {{.*}}/swift-autolink-extract{{.*}}
+// CHECK: {{.*}}swift_begin.o /{{.*}}/linker-args-order-linux-{{[a-z0-9]+}}.o @/{{.*}}/linker-args-order-linux-{{[a-z0-9]+}}.autolink {{.*}} @{{.*}}/static-stdlib-args.lnk {{.*}} -Xlinker --no-allow-multiple-definition {{.*}}/swift_end.o