Revert r260266 (and r260276), "clang-cl: Enable plugins on Windows"

It doesn't work, at least, i686-win32.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@260537 91177308-0d34-0410-b5e6-96231b3b80d8

test/Frontend/plugins.c

@@ -1,5 +1,4 @@
 // RUN: %clang_cc1 -load %llvmshlibdir/PrintFunctionNames%pluginext -plugin print-fns %s 2>&1 | FileCheck %s
-// RUN: %clang_cl -c -Xclang -load -Xclang %llvmshlibdir/PrintFunctionNames%pluginext -Xclang -plugin -Xclang print-fns -Tc %s 2>&1 | FileCheck %s
 // REQUIRES: plugins, examples
 
 // CHECK: top-level-decl: "x"

test/lit.cfg

@@ -196,7 +196,7 @@ if not lit_config.quiet:
 
 # Plugins (loadable modules)
 # TODO: This should be supplied by Makefile or autoconf.
-if sys.platform in ['cygwin']:
+if sys.platform in ['win32', 'cygwin']:
     has_plugins = (config.enable_shared == 1)
 else:
     has_plugins = True