CMake Crosscompile nach embeded Linux

[operator (Gast)]

Ich sitze nun schon einige Zeit an CMake und versuche mein Programm auf 
ein embedded Linux crosscompilieren.

Meine Ordnerstruktur sieht folgendermassen aus:

Topdir/
  -CMakeLists.txt
  -toolchain-arm-angstrom-linux-gnueabi.cmake
  +build/
  +src/
    -CMakeLists.txt
    -sourcefiles.cpp
    -headerfiles.h
  +gen/
    -CMakeLists.txt
    -sourcefiles.cpp
    -headerfiles.h
  +libs/
    -CMakeLists.txt
    +subfolders/

Im buildverzeichnis rufe ich $ cmake .. auf und danach $ make. Dies 
funktioniert einwandfrei und ich kann nativ für x86 die Library builden.
Wenn ich aber mittels

$ cmake -DCMAKE_TOOLCHAIN_FILE=../toolchain-arm-angstrom-linux-gnueabi.cmake .. 
$ make

ausführe kommt folgende Fehlermeldung:

In file included from /home/user/cmake/topdir/src/ComponentImpl.h:11:0,
                 from /home/user/cmake/topdir/src/ComponentImpl.cpp:8:
/home/user/cmake/topdir/src/IComponent.hpp:11:18: fatal error: string: No such file or directory
compilation terminated.
make[2]: *** [CMakeFiles/topdir.dir/src/ComponentImpl.cpp.o] Error 1
make[1]: *** [CMakeFiles/topdir.dir/all] Error 2
make: *** [all] Error 2

Ich komme aber einfach nicht darauf woran das liegen kann. Anbei die 
erste CMakeLists.txt aus topdir/

# Minimal required CMake-Version
cmake_minimum_required(VERSION 2.6)

# Name project and select toolchain
project (IFM2-Infrastructure)
set(CMAKE_BUILD_TYPE Debug)
set(CMAKE_SYSTEM_NAME Linux)

# CMake should also search in this subfolders for CMakeLists
add_subdirectory(src)
add_subdirectory(gen)
add_subdirectory(libs)

# Include Files are located in
include_directories("src")
include_directories("gen")
include_directories("libs")

#Collect variable names from subdirs
set(libSrcs 
  ${library_IFM2SRC} 
  ${library_IFM2GEN} 
  ${library_IFM2LIBS} 
)

#Compiler flags
set(CMAKE_CXX_FLAGS "-g -Wall")
set(BUILD_SHARED_LIBS ON)

#create library and link it to other
set(LIBRARY_OUTPUT_PATH ${PROJECT_BINARY_DIR}/out)
add_library(IFM2-Infrastructure SHARED ${libSrcs})
target_link_libraries(IFM2-Infrastructure -lrt -lpthread)

und das toolchain file

# this one is important
set(CMAKE_SYSTEM_NAME Linux)

INCLUDE(CMakeForceCompiler)
# specify the cross compiler
CMAKE_FORCE_C_COMPILER(/local/build/aba/bebuild21/toolchain/sysroots/i686-angstromsdk-linux/usr/bin/armv7ahf-vfp-neon-angstrom-linux-gnueabi/arm-angstrom-linux-gnueabi-gcc GNU)
CMAKE_FORCE_CXX_COMPILER(/local/build/aba/bebuild21/toolchain/sysroots/i686-angstromsdk-linux/usr/bin/armv7ahf-vfp-neon-angstrom-linux-gnueabi/arm-angstrom-linux-gnueabi-g++ GNU)

# where is the target environment 
set(CMAKE_FIND_ROOT_PATH 
  /local/build/aba/bebuild21/toolchain/sysroots/armv7ahf-vfp-neon-angstrom-linux-gnueabi
)

# search for programs in the build host directories
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
# for libraries and headers in the target directories
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)