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

[Pascal Bach]

This already got fixed in the toolchain file that is used during development
in https://github.com/openembedded/openembedded-core/commit/cb42802f2fe1760f894a435b07286bca3a220364

The toolchain file generated by the cmake.bbclass however does not set
CMAKE_SYSROOT. Under certain circumstances this also leads to the error:
`"stdlib.h: No such file or directory #include_next <stdlib.h>"`
during the build of a recipe.

An example where this accured was during the upgrade of the Apache Thrift
recipe in meta-openembedded to 0.11.0. With this change the build works out of
the box.

CMAKE_SYSROOT must only be set when crosscompiling, otherwise it will interfere
with the native compiler headers.

Signed-off-by: Pascal Bach <pascal.bach at siemens.com>
---
 meta/classes/cmake.bbclass | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/meta/classes/cmake.bbclass b/meta/classes/cmake.bbclass
index fd40a9863e..251ddd9afe 100644
--- a/meta/classes/cmake.bbclass
+++ b/meta/classes/cmake.bbclass
@@ -64,9 +64,12 @@ def map_target_arch_to_uname_arch(target_arch):
         return "ppc64"
     return target_arch
 
+
 cmake_do_generate_toolchain_file() {
 	if [ "${BUILD_SYS}" = "${HOST_SYS}" ]; then
 		cmake_crosscompiling="set( CMAKE_CROSSCOMPILING FALSE )"
+	else
+		cmake_sysroot="set( CMAKE_SYSROOT \"${RECIPE_SYSROOT}\" )"
 	fi
 	cat > ${WORKDIR}/toolchain.cmake <<EOF
 # CMake system name must be something like "Linux".
@@ -95,6 +98,8 @@ set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM ${OECMAKE_FIND_ROOT_PATH_MODE_PROGRAM} )
 set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
 set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )
 
+$cmake_sysroot
+
 # Use qt.conf settings
 set( ENV{QT_CONF_PATH} ${WORKDIR}/qt.conf )
 
-- 
2.11.0