MSVC: Use dubbed FH4 to make C++ exception handling smaller

Visual Studio 2019 introduced the dubbed FH4 feature
which can make C++ exception handling smaller on x64.
According to the article [1], it's enabled by default
for UWP applications, and Microsoft also use it in
their own widely-known commercial products such as
Office to reduce the binary size.

So make use of this feature for Qt when possible, to
get smaller binary.

As a drive-by, add "/EHs-c-" explicitly to the flags
when we want to disable C++ exception handling.

[1] Official article that introduces dubbed FH4:
https://devblogs.microsoft.com/cppblog/making-cpp-exception-handling-smaller-x64/

Change-Id: I2e3330de477f78372cf7903d0ef7a732b09552a9
Reviewed-by: Thiago Macieira <[email protected]>
Reviewed-by: André de la Rocha <[email protected]>
Reviewed-by: Qt CI Bot <[email protected]>
Reviewed-by: Oliver Wolff <[email protected]>

cmake/QtFlagHandlingHelpers.cmake

@@ -148,16 +148,19 @@ function(qt_internal_set_exceptions_flags target exceptions_on)
     if(exceptions_on)
         if(MSVC)
             set(_flag "/EHsc")
+            if(MSVC_VERSION GREATER_EQUAL 1929)
+                set(_flag ${_flag} "/d2FH4")
+            endif()
         endif()
     else()
         set(_defs "QT_NO_EXCEPTIONS")
         if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-            set(_flag "/wd4530" "/wd4577")
+            set(_flag "/EHs-c-" "/wd4530" "/wd4577")
         elseif ("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU|AppleClang|InteLLLVM")
             set(_flag "-fno-exceptions")
         elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
             if (MSVC)
-                set(_flag "/wd4530" "/wd4577")
+                set(_flag "/EHs-c-" "/wd4530" "/wd4577")
             else()
                 set(_flag "-fno-exceptions")
             endif()