Disable 03/11 tests under Clang/Win

appveyor.yml

@@ -14,6 +14,10 @@ branches:
 
 environment:
   matrix:
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      TOOLSET: clang
+      CXXSTD: 14
+      CLANG_WIN: 1
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
       TOOLSET: msvc-9.0
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
@@ -57,9 +61,6 @@ environment:
       ADDPATH: C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin;
       TOOLSET: gcc
       CXXSTD: 03,11
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: clang
-      CXXSTD: 14
 
 install:
   - set BOOST_BRANCH=develop

test/Jamfile.v2

@@ -76,11 +76,12 @@ project
       return $(result) ;
    }
 
-if [ os.environ UBSAN ]
+if [ os.environ UBSAN ] || [ os.environ CLANG_WIN ]
 {
    rule system-run ( sources + )
    {
       # The 03/11 tests are ODR violations, no point running them under -fsanitize=undefined
+      # Clang on Windows uses MSVC headers, which don't parse under 03/11
       return [ system-run- $(sources) ] ;
    }
 }