[test] Don't actually emit a .so for autolink-extract tests (#17938)

Two tests used -emit-library with the same module name and without an
explicit -o path, meaning that the output would go into whatever
lit.py was using as its working directory. If the tests ran at exactly
the same time, they could contend for the output file. We don't actually
use the built library at all in the test, so just drop the -emit-library
entirely.

Also, remove an unused compilation step from another test, which just
checks what happens when swift-autolink-extract doesn't use any
arguments.

rdar://problem/39510413

test/AutolinkExtract/error_no_inputs.swift

@@ -1,4 +1,3 @@
-// RUN: %target-swiftc_driver -c %s -o %t
 // RUN: not %target-swift-autolink-extract 2>&1 | %FileCheck %s
 
 // REQUIRES: autolink-extract

test/AutolinkExtract/import.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swiftc_driver -emit-library -emit-module -emit-module-path %t/empty.swiftmodule -module-name empty -module-link-name empty %S/empty.swift
+// RUN: %target-swiftc_driver -emit-module -emit-module-path %t/empty.swiftmodule -module-name empty -module-link-name empty %S/empty.swift
 // RUN: %target-swiftc_driver -c %s -I %t -o %t/import_experimental.o
 // RUN: %target-swift-autolink-extract %t/import_experimental.o -o - | %FileCheck --check-prefix CHECK-%target-object-format %s
 

test/AutolinkExtract/import_archive.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swiftc_driver -emit-library -emit-module -emit-module-path %t/empty.swiftmodule -module-name empty -module-link-name empty %S/empty.swift
+// RUN: %target-swiftc_driver -emit-module -emit-module-path %t/empty.swiftmodule -module-name empty -module-link-name empty %S/empty.swift
 // RUN: %target-swiftc_driver -c %s -I %t -o %t/import_experimental.o
 // RUN: llvm-ar cr %t/import_experimental.a %t/import_experimental.o
 // RUN: %target-swift-autolink-extract %t/import_experimental.a -o - | %FileCheck --check-prefix CHECK-%target-object-format %s