[LyX/master] Do not use --std=c++14 for MSVC

[Georg Baum]

commit 987dd8446131ab638217be9f7d29e17f87bf3e39
Author: Georg Baum <b...@lyx.org>
Date:   Sat Jul 2 12:42:04 2016 +0200

    Do not use --std=c++14 for MSVC
    
    MSVC does not need a special flag to specify the standard. Using --std=c++14
    produces a warning, but compilation succeeds, so the old code did mistakenly
    choose --std=c++14 for MSVC.
---
 development/cmake/modules/FindCXX11Compiler.cmake |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/development/cmake/modules/FindCXX11Compiler.cmake 
b/development/cmake/modules/FindCXX11Compiler.cmake
index 56fa0c3..c7045d1 100644
--- a/development/cmake/modules/FindCXX11Compiler.cmake
+++ b/development/cmake/modules/FindCXX11Compiler.cmake
@@ -40,12 +40,19 @@ else()
   if (CYGWIN)
     set(CXX11_FLAG_CANDIDATES "--std=gnu++11")
   else()
-    set(CXX11_FLAG_CANDIDATES
-      "--std=c++14"
-      "--std=c++11"
-      "--std=gnu++11"
-      "--std=gnu++0x"
-    )
+    if (MSVC)
+      # MSVC does not have a general C++11 flag, one can only switch off
+      # MS extensions with /Za in general or by extension with /Zc.
+      # Use an empty flag to ensure that CXX11_STD_REGEX is correctly set.
+      set(CXX11_FLAG_CANDIDATES "")
+    else()
+      set(CXX11_FLAG_CANDIDATES
+        "--std=c++14"
+        "--std=c++11"
+        "--std=gnu++11"
+        "--std=gnu++0x"
+      )
+    endif()
   endif()
 endif()