Retire VS2015 Support

As proposed here: https://lists.llvm.org/pipermail/llvm-dev/2019-June/133147.html

This patch raises the minimum supported version to build LLVM/Clang to Visual Studio 2017.

Differential Revision: https://reviews.llvm.org/D64326

llvm-svn: 365452
diff --git a/llvm/cmake/modules/CheckCompilerVersion.cmake b/llvm/cmake/modules/CheckCompilerVersion.cmake
index 1ee7832..2f4d75f 100644
--- a/llvm/cmake/modules/CheckCompilerVersion.cmake
+++ b/llvm/cmake/modules/CheckCompilerVersion.cmake
@@ -10,7 +10,10 @@
 set(CLANG_SOFT_ERROR 3.5)
 set(APPLECLANG_MIN 3.1)
 set(APPLECLANG_SOFT_ERROR 6.0)
-set(MSVC_MIN 19.00.24213.1)
+
+# https://en.wikipedia.org/wiki/Microsoft_Visual_C#Internal_version_numbering
+# _MSC_VER == 1910 MSVC++ 14.1 (Visual Studio 2017 version 15.0)
+set(MSVC_MIN 19.1)
 set(MSVC_SOFT_ERROR 19.1)
 
 # Map the above GCC versions to dates: https://gcc.gnu.org/develop.html#timeline