CMake: Fix sanitizer build when using Clang on Linux

Apparently the combination of the --no-undefined linker flag together
with ASAN when building on Linux with Clang does not work.

Disable --no-undefined flag in such a scenario. Note that linux-clang
mkspec doesn't add that flag at all, which is why asan builds work
there.

Change-Id: I6167c757ce4be5d2263311bc84e5fb445b0f7c2d
Fixes: QTBUG-86879
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

cmake/QtFlagHandlingHelpers.cmake

@@ -51,6 +51,9 @@ function(qt_internal_add_link_flags_no_undefined target)
         return()
     endif()
     if (GCC OR CLANG)
+        if(CLANG AND QT_FEATURE_sanitizer)
+            return()
+        endif()
         set(previous_CMAKE_REQUIRED_LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
 
         set(CMAKE_REQUIRED_LINK_OPTIONS "-Wl,-undefined,error")