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如果在编译时指定了-sysroot就是为编译时指定了逻辑目录。编译过程中需要引用的库，头文件，如果要到/usr/include目录下去找的情况下，则会在前面加上逻辑目录。
如此处我们指定 -sysroot=/home/shell.albert/tools/toolschain_arm/4.4.3/arm-none-Linux-gnueabi/sys-root
则如果在编译过程中需要找stdio.h，则会用/usr/include/目录下去找，因为我们指定了系统目录，则会到下面的路径去找。
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/usr/include> pwd
/home/shell.albert/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/usr/include
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/usr/include> ls -l stdio.h
-r--r--r-- 1 shell.albert users 31052 Jul 24 2010 stdio.h
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/usr/include>
当然，如果我们同时指定了--prefix=/home/shell.albert/libqt5.3.2希望生成的库和头文件等都安装到此目录下，执行make install开始复制操作。
但是当我们去系统的/home/shell.albert/libqt5.3.2中去寻找编译成果时却没有这些文件，
而直接的成果输出在了，输出路径是相对于-sysroot的。
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/home/shell.albert/libqt5.3.2> pwd
/home/shell.albert/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/home/shell.albert/libqt5.3.2
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/home/shell.albert/libqt5.3.2> ls
bin doc imports include lib phrasebooks plugins qml translations
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/home/shell.albert/libqt5.3.2> ls lib
cmake libQt5Designer.so.5.3.2 libQt5Positioning.so.5 libQt5Sql.so.5.3
fonts libQt5Gui.la libQt5Positioning.so.5.3 libQt5Sql.so.5.3.2
libQt5Bluetooth.la libQt5Gui.prl libQt5Positioning.so.5.3.2 libQt5Svg.la
libQt5Bluetooth.prl libQt5Gui.so libQt5PrintSupport.la libQt5Svg.prl
libQt5Bluetooth.so libQt5Gui.so.5 libQt5PrintSupport.prl libQt5Svg.so
libQt5Bluetooth.so.5 libQt5Gui.so.5.3 libQt5PrintSupport.so libQt5Svg.so.5
libQt5Bluetooth.so.5.3 libQt5Gui.so.5.3.2 libQt5PrintSupport.so.5 libQt5Svg.so.5.3
libQt5Bluetooth.so.5.3.2 libQt5Help.la libQt5PrintSupport.so.5.3 libQt5Svg.so.5.3.2
libQt5CLucene.la libQt5Help.prl libQt5PrintSupport.so.5.3.2 libQt5Test.la
libQt5CLucene.prl libQt5Help.so libQt5Qml.la libQt5Test.prl
libQt5CLucene.so libQt5Help.so.5 libQt5Qml.prl libQt5Test.so
libQt5CLucene.so.5 libQt5Help.so.5.3 libQt5Qml.so libQt5Test.so.5
libQt5CLucene.so.5.3 libQt5Help.so.5.3.2 libQt5Qml.so.5 libQt5Test.so.5.3
libQt5CLucene.so.5.3.2 libQt5Multimedia.la libQt5Qml.so.5.3 libQt5Test.so.5.3.2
libQt5Concurrent.la libQt5Multimedia.prl libQt5Qml.so.5.3.2 libQt5UiTools.a
libQt5Concurrent.prl libQt5Multimedia.so libQt5Script.la libQt5UiTools.la
libQt5Concurrent.so libQt5Multimedia.so.5 libQt5Script.prl libQt5UiTools.prl
libQt5Concurrent.so.5 libQt5Multimedia.so.5.3 libQt5Script.so libQt5WebSockets.la
libQt5Concurrent.so.5.3 libQt5Multimedia.so.5.3.2 libQt5Script.so.5 libQt5WebSockets.prl
libQt5Concurrent.so.5.3.2 libQt5MultimediaWidgets.la libQt5Script.so.5.3 libQt5WebSockets.so
libQt5Core.la libQt5MultimediaWidgets.prl libQt5Script.so.5.3.2 libQt5WebSockets.so.5
libQt5Core.prl libQt5MultimediaWidgets.so libQt5ScriptTools.la libQt5WebSockets.so.5.3
libQt5Core.so libQt5MultimediaWidgets.so.5 libQt5ScriptTools.prl libQt5WebSockets.so.5.3.2
libQt5Core.so.5 libQt5MultimediaWidgets.so.5.3 libQt5ScriptTools.so libQt5Widgets.la
libQt5Core.so.5.3 libQt5MultimediaWidgets.so.5.3.2 libQt5ScriptTools.so.5 libQt5Widgets.prl
libQt5Core.so.5.3.2 libQt5Network.la libQt5ScriptTools.so.5.3 libQt5Widgets.so
libQt5Declarative.la libQt5Network.prl libQt5ScriptTools.so.5.3.2 libQt5Widgets.so.5
libQt5Declarative.prl libQt5Network.so libQt5Sensors.la libQt5Widgets.so.5.3
libQt5Declarative.so libQt5Network.so.5 libQt5Sensors.prl libQt5Widgets.so.5.3.2
libQt5Declarative.so.5 libQt5Network.so.5.3 libQt5Sensors.so libQt5Xml.la
libQt5Declarative.so.5.3 libQt5Network.so.5.3.2 libQt5Sensors.so.5 libQt5XmlPatterns.la
libQt5Declarative.so.5.3.2 libQt5Nfc.la libQt5Sensors.so.5.3 libQt5XmlPatterns.prl
libQt5DesignerComponents.la libQt5Nfc.prl libQt5Sensors.so.5.3.2 libQt5XmlPatterns.so
libQt5DesignerComponents.prl libQt5Nfc.so libQt5SerialPort.la libQt5XmlPatterns.so.5
libQt5DesignerComponents.so libQt5Nfc.so.5 libQt5SerialPort.prl libQt5XmlPatterns.so.5.3
libQt5DesignerComponents.so.5 libQt5Nfc.so.5.3 libQt5SerialPort.so libQt5XmlPatterns.so.5.3.2
libQt5DesignerComponents.so.5.3 libQt5Nfc.so.5.3.2 libQt5SerialPort.so.5 libQt5Xml.prl
libQt5DesignerComponents.so.5.3.2 libQt5PlatformSupport.a libQt5SerialPort.so.5.3 libQt5Xml.so
libQt5Designer.la libQt5PlatformSupport.la libQt5SerialPort.so.5.3.2 libQt5Xml.so.5
libQt5Designer.prl libQt5PlatformSupport.prl libQt5Sql.la libQt5Xml.so.5.3
libQt5Designer.so libQt5Positioning.la libQt5Sql.prl libQt5Xml.so.5.3.2
libQt5Designer.so.5 libQt5Positioning.prl libQt5Sql.so pkgconfig
libQt5Designer.so.5.3 libQt5Positioning.so libQt5Sql.so.5
shell.albert@yantai:~/tools/toolschain_arm/4.4.3/arm-none-linux-gnueabi/sys-root/home/shell.albert/libqt5.3.2>