Tests: Teach tests when to treat clang-cl as MSVC

* Disable the system include unused variable test in ExportImport when
  clang is in MSVC compatible mode.

* Disable CxxDialect testcase when clang is in MSVC compatible mode, as
  it doesn't support `typeof`.

* Teach Module.WriteCompilerDetectionHeader to treat clang-cl as MSVC.

* Disable the SystemIncludeDirectories testcase within
  IncludeDirectories when clang is in MSVC compatible mode.

* Disable the CMakeOnly.CheckCXXCompilerFlag testcase when clang is in
  MSVC compatible mode.

* Treat clang-cl as MSVC in LinkOptions.cmake in the try_run and
  try_compile testcases.
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index e8e5a2c..40e53a2 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -459,7 +459,7 @@
     set(runCxxDialectTest 1)
   endif()
   if(CMAKE_CXX_COMPILER_ID STREQUAL Clang
-        AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
+        AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4 AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
     if(NOT APPLE OR POLICY CMP0025)
       set(runCxxDialectTest 1)
     endif()
diff --git a/Tests/CMakeOnly/CheckCXXCompilerFlag/CMakeLists.txt b/Tests/CMakeOnly/CheckCXXCompilerFlag/CMakeLists.txt
index 9be69f1..1f9d3ac 100644
--- a/Tests/CMakeOnly/CheckCXXCompilerFlag/CMakeLists.txt
+++ b/Tests/CMakeOnly/CheckCXXCompilerFlag/CMakeLists.txt
@@ -57,7 +57,7 @@
   message("Unhandled Platform")
 endif()
 
-if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang" AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
   check_cxx_compiler_flag("-x c++" HAVE_X_CXX)
   if(NOT HAVE_X_CXX)
     message(FATAL_ERROR "${CMAKE_CXX_COMPILER_ID} compiler flag '-x c++' check failed")
diff --git a/Tests/ExportImport/Import/A/CMakeLists.txt b/Tests/ExportImport/Import/A/CMakeLists.txt
index 811fff3..b5df961 100644
--- a/Tests/ExportImport/Import/A/CMakeLists.txt
+++ b/Tests/ExportImport/Import/A/CMakeLists.txt
@@ -407,7 +407,7 @@
 unset(_configs)
 
 if (((CMAKE_C_COMPILER_ID STREQUAL GNU AND CMAKE_C_COMPILER_VERSION VERSION_GREATER 4.4)
-    OR CMAKE_C_COMPILER_ID STREQUAL Clang)
+    OR (CMAKE_C_COMPILER_ID STREQUAL Clang AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC"))
     AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles" OR CMAKE_GENERATOR STREQUAL "Ninja"))
   include(CheckCXXCompilerFlag)
   check_cxx_compiler_flag(-Wunused-variable run_sys_includes_test)
diff --git a/Tests/IncludeDirectories/CMakeLists.txt b/Tests/IncludeDirectories/CMakeLists.txt
index b7b8320..761c405 100644
--- a/Tests/IncludeDirectories/CMakeLists.txt
+++ b/Tests/IncludeDirectories/CMakeLists.txt
@@ -2,7 +2,7 @@
 project(IncludeDirectories)
 
 if (((CMAKE_C_COMPILER_ID STREQUAL GNU AND CMAKE_C_COMPILER_VERSION VERSION_GREATER 4.4)
-    OR CMAKE_C_COMPILER_ID STREQUAL Clang OR CMAKE_C_COMPILER_ID STREQUAL AppleClang)
+    OR (CMAKE_C_COMPILER_ID STREQUAL Clang AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC") OR CMAKE_C_COMPILER_ID STREQUAL AppleClang)
     AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles"
       OR CMAKE_GENERATOR STREQUAL "Ninja"
       OR (CMAKE_GENERATOR STREQUAL "Xcode" AND NOT XCODE_VERSION VERSION_LESS 6.0)))
diff --git a/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt b/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
index 45bb229..616092d 100644
--- a/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
+++ b/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
@@ -61,7 +61,7 @@
   string(REGEX REPLACE "^[0-9]+\\.[0-9]+\\.([0-9]+).*" "\\1" COMPILER_VERSION_PATCH "${CMAKE_C_COMPILER_VERSION}")
 
   if (CMAKE_C_COMPILER_ID STREQUAL "GNU"
-      OR CMAKE_C_COMPILER_ID STREQUAL "Clang"
+      OR (CMAKE_C_COMPILER_ID STREQUAL "Clang" AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
       OR CMAKE_C_COMPILER_ID STREQUAL "AppleClang"
       OR CMAKE_C_COMPILER_ID STREQUAL "Intel")
     add_executable(WriteCompilerDetectionHeader_C11 main.c)
@@ -118,7 +118,7 @@
 string(REGEX REPLACE "^[0-9]+\\.[0-9]+\\.([0-9]+).*" "\\1" COMPILER_VERSION_PATCH "${CMAKE_CXX_COMPILER_VERSION}")
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU"
-    OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang"
+    OR (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
     OR CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang"
     OR CMAKE_CXX_COMPILER_ID STREQUAL "SunPro"
     OR CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
@@ -128,7 +128,7 @@
 endif()
 
 # for msvc the compiler version determines which c++11 features are available.
-if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" OR "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
   if(";${CMAKE_CXX_COMPILE_FEATURES};" MATCHES ";cxx_delegating_constructors;")
     list(APPEND true_defs EXPECTED_COMPILER_CXX_DELEGATING_CONSTRUCTORS)
     list(APPEND true_defs EXPECTED_COMPILER_CXX_VARIADIC_TEMPLATES)
diff --git a/Tests/RunCMake/try_compile/LinkOptions.cmake b/Tests/RunCMake/try_compile/LinkOptions.cmake
index 9b246c4..488cab1 100644
--- a/Tests/RunCMake/try_compile/LinkOptions.cmake
+++ b/Tests/RunCMake/try_compile/LinkOptions.cmake
@@ -5,7 +5,7 @@
 
 set (lib_name "${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}lib${CMAKE_STATIC_LIBRARY_SUFFIX}")
 if (CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  if (RunCMake_C_COMPILER_ID STREQUAL "MSVC")
+  if (RunCMake_C_COMPILER_ID STREQUAL "MSVC" OR "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
     if (CMAKE_SIZEOF_VOID_P EQUAL 4)
       set (undef_flag /INCLUDE:_func)
     else()
diff --git a/Tests/RunCMake/try_run/LinkOptions.cmake b/Tests/RunCMake/try_run/LinkOptions.cmake
index 17af2f7..9939a42 100644
--- a/Tests/RunCMake/try_run/LinkOptions.cmake
+++ b/Tests/RunCMake/try_run/LinkOptions.cmake
@@ -5,7 +5,7 @@
 
 set (lib_name "${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}lib${CMAKE_STATIC_LIBRARY_SUFFIX}")
 if (CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  if (RunCMake_C_COMPILER_ID STREQUAL "MSVC")
+  if (RunCMake_C_COMPILER_ID STREQUAL "MSVC" OR "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
     if (CMAKE_SIZEOF_VOID_P EQUAL 4)
       set (undef_flag /INCLUDE:_func)
     else()