llvm-lto2: Move the LTO::run() action behind a subcommand.

Move LTO::run() to a "run" subcommand so that we can introduce new subcommands
for testing different parts of the LTO implementation.

This doesn't use llvm::cl subcommands because it doesn't appear to be currently
possible to pass an argument not associated with a subcommand to a subcommand
(e.g. -lto-use-new-pm, -mcpu=yonah).

Differential Revision: https://reviews.llvm.org/D31410

llvm-svn: 299967
diff --git a/llvm/test/LTO/Resolution/X86/commons.ll b/llvm/test/LTO/Resolution/X86/commons.ll
index b3e5048..28bf1ad 100644
--- a/llvm/test/LTO/Resolution/X86/commons.ll
+++ b/llvm/test/LTO/Resolution/X86/commons.ll
@@ -1,6 +1,6 @@
 ; RUN: llvm-as -o %t1.bc %s
 ; RUN: llvm-as -o %t2.bc %p/Inputs/commons.ll
-; RUN: llvm-lto2 %t1.bc -r=%t1.bc,x,l %t2.bc -r=%t2.bc,x,pl -o %t.out -save-temps
+; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,x,l %t2.bc -r=%t2.bc,x,pl -o %t.out -save-temps
 ; RUN: llvm-dis -o - %t.out.0.0.preopt.bc  | FileCheck %s
 
 ; A strong definition should override the common