Fix build with Ninja generator

Summary:
We were hitting a bug in CMake's Ninja generator that was causing it to incorrectly attempt to escape the closing quote on `_HAS_AUTO_PTR_ETC=1`, so remove the quotes, as they aren't actually needed.
This also makes a few quality-of-life changes to make building Folly with Ninja slightly easier.

Closes: https://github.com/facebook/folly/issues/604

Reviewed By: yfeldblum

Differential Revision: D5134585

fbshipit-source-id: 3816e53774f7963b9b4fd8ddf68b83ff7afdefe1

CMake/FollyCompiler.cmake

@@ -43,6 +43,20 @@ if (MSVC_USE_STATIC_RUNTIME)
   endforeach()
 endif()
 
+# The Ninja generator doesn't de-dup the exception mode flag, so remove the
+# default flag so that MSVC doesn't warn about it on every single file.
+if ("${CMAKE_GENERATOR}" STREQUAL "Ninja")
+  foreach(flag_var
+      CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE
+      CMAKE_C_FLAGS_MINSIZEREL CMAKE_C_FLAGS_RELWITHDEBINFO
+      CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+      CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+    if (${flag_var} MATCHES "/EHsc")
+      string(REGEX REPLACE "/EHsc" "" ${flag_var} "${${flag_var}}")
+    endif()
+  endforeach()
+endif()
+
 # In order for /Zc:inline, which speeds up the build significantly, to work
 # we need to remove the /Ob0 parameter that CMake adds by default, because that
 # would normally disable all inlining.
@@ -241,8 +255,8 @@ function(apply_folly_compile_options_to_target THETARGET)
       
       _STL_EXTRA_DISABLED_WARNINGS=4774\ 4987
 
-      $<$<BOOL:${MSVC_ENABLE_CPP_LATEST}>:"_HAS_AUTO_PTR_ETC=1"> # We're building in C++ 17 or greater mode, but certain dependencies (Boost) still have dependencies on unary_function and binary_function, so we have to make sure not to remove them.
-      $<$<BOOL:${MSVC_ENABLE_LEAN_AND_MEAN_WINDOWS}>:"WIN32_LEAN_AND_MEAN"> # Don't include most of Windows.h
+      $<$<BOOL:${MSVC_ENABLE_CPP_LATEST}>:_HAS_AUTO_PTR_ETC=1> # We're building in C++ 17 or greater mode, but certain dependencies (Boost) still have dependencies on unary_function and binary_function, so we have to make sure not to remove them.
+      $<$<BOOL:${MSVC_ENABLE_LEAN_AND_MEAN_WINDOWS}>:WIN32_LEAN_AND_MEAN> # Don't include most of Windows.h
   )
 
   # Ignore a warning about an object file not defining any symbols,

CMakeLists.txt

@@ -11,6 +11,9 @@ if ("${CMAKE_GENERATOR}" MATCHES "Visual Studio 15( 2017)? Win64")
 elseif ("${CMAKE_GENERATOR}" STREQUAL "Visual Studio 14 2015 Win64")
   set(CMAKE_GENERATOR_TOOLSET "v140</PlatformToolset></PropertyGroup><ItemDefinitionGroup Condition=\"'$(ProjectName)'=='folly'\"><ProjectReference><LinkLibraryDependencies>true</LinkLibraryDependencies></ProjectReference></ItemDefinitionGroup><PropertyGroup><PlatformToolset>v140")
   set(MSVC_IS_2017 OFF)
+elseif ("${CMAKE_GENERATOR}" STREQUAL "Ninja")
+  message("Folly is being built with Ninja, so assuming VS 2017 is being used.")
+  set(MSVC_IS_2017 ON)
 else()
   message(FATAL_ERROR "This build script only supports building Folly on 64-bit Windows with Visual Studio 2015 or Visual Studio 2017.")
 endif()