Remove a gross usage of environment variables in MachineVerifier, replacing it with support for setting the -verify-machineinstrs flag via an environment variable in LIT.

This preserves the handy functionality of force-enabling the MachineVerifier, without the need to embed usage of environment variables in LLVM client applications.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228079 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/Passes.cpp

@@ -81,7 +81,9 @@ static cl::opt<bool> PrintGCInfo("print-gc", cl::Hidden,
     cl::desc("Dump garbage collector data"));
 static cl::opt<bool> VerifyMachineCode("verify-machineinstrs", cl::Hidden,
     cl::desc("Verify generated machine code"),
-    cl::init(getenv("LLVM_VERIFY_MACHINEINSTRS")!=nullptr));
+    cl::init(false),
+    cl::ZeroOrMore);
+
 static cl::opt<std::string>
 PrintMachineInstrs("print-machineinstrs", cl::ValueOptional,
                    cl::desc("Print machine instrs"),