title: Qt cannot find the standard header
body: <p>The compilation is failing due to standard Qt include files/ library missing, why?</p>
  
  <p>I have custom toolchain for devices. My compilation fails with messages:</p>
  
  <p><strong>In file included from /opt/STM/STLinux-2.3/devkit/sh4/target/usr/include/QtCore/QString:1:0,
                   from ./menuitems/Item.h:5,
                   from ./appmessages/AppMessageAgeLimit.h:4,
                   from appmessages/AMessageDispatcher.cpp:2:
  /opt/STM/STLinux-2.3/devkit/sh4/target/usr/include/QtCore/qstring.h:60:22: fatal error: string: No such file or directory</strong></p>
  
  <p>It guess that this toolchain has been configured wrong but I don't know how to fix it. Below is output from "/opt/STM/STLinux-2.3/devkit/sh4/bin/sh4-linux-g++ -v" command - may be it will be useful:</p>
  
  <p><em>Using built-in specs.
  COLLECT_GCC=/opt/STM/STLinux-2.3/devkit/sh4/bin/sh4-linux-g++
  COLLECT_LTO_WRAPPER=/opt/STM/STLinux-2.3/devkit/sh4/libexec/gcc/sh4-linux/4.8.2/lto-wrapper
  Target: sh4-linux
  Configured with: /home/viatcheslavvgavrilov/qt/gcc-4.8.2/configure --target=sh4-linux --prefix=/opt/STM/STLinux-2.3/devkit/sh4 --exec-prefix=/opt/STM/STLinux-2.3/devkit/sh4 --bindir=/opt/STM/STLinux-2.3/devkit/sh4/bin --sbindir=/opt/STM/STLinux-2.3/devkit/sh4/sbin --sysconfdir=/opt/STM/STLinux-2.3/devkit/sh4/etc --datadir=/opt/STM/STLinux-2.3/devkit/sh4/share --includedir=/opt/STM/STLinux-2.3/devkit/sh4/include --libdir=/opt/STM/STLinux-2.3/devkit/sh4/lib --libexecdir=/opt/STM/STLinux-2.3/devkit/sh4/libexec --localstatedir=/opt/STM/STLinux-2.3/devkit/sh4/var --sharedstatedir=/opt/STM/STLinux-2.3/devkit/sh4/share --mandir=/opt/STM/STLinux-2.3/devkit/sh4/man --infodir=/opt/STM/STLinux-2.3/devkit/sh4/info --enable-checking=assert --program-prefix=sh4-linux- --with-local-prefix=/opt/STM/STLinux-2.3/devkit/sh4 --with-sysroot=/opt/STM/STLinux-2.3/devkit/sh4/target --enable-languages=c,c++ --enable-threads=posix --enable-nls --enable-c99 --enable-long-long --with-system-zlib --enable-shared --disable-libgomp --enable-multilib --with-multilib-list=m4,m4-nofpu --enable-symvers=gnu --with-gxx-include-dir=/target/usr/include/c++/4.2.4 --enable-__cxa_atexit
  Thread model: posix
  gcc version 4.8.2 20131016 (GCC)</em> </p>