[OE-core] [PATCH] cmake: add CMAKE_SYSROOT to generated toolchain file

[Mikko.Rapeli at bmw.de]

> Fixes problems which we have also seen on sumo branch. Thanks for this!

Sorry, spoke too soon. This fixes compilation on a few recipes in my tree
but there are still lots failures with the same error message. We had a hacky
patch to cmake as a workaround but that too causes some problems:

--- a/Modules/Compiler/GNU.cmake
+++ b/Modules/Compiler/GNU.cmake
@@ -45,7 +45,7 @@
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
   if(NOT APPLE OR NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4) # work around #4462
-    set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
+    set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-I ")
   endif()
 
   set(_CMAKE_${lang}_IPO_SUPPORTED_BY_CMAKE YES)

I wonder what the real fix could be...

-Mikko