docs/buildroot: use DESTDIR / install-strip for target install example

    <a name="ex2line34" id="ex2line34">34</a>          $(MAKE) CC=$(TARGET_CC) -C $(FOO_DIR)

    <a name="ex2line35" id="ex2line35">35</a>

    <a name="ex2line36" id="ex2line36">36</a>  $(TARGET_DIR)/$(FOO_TARGET_BINARY): $(FOO_DIR)/$(FOO_BINARY)

    <a name="ex2line37" id="ex2line37">37</a>          $(MAKE) prefix=$(TARGET_DIR)/usr -C $(FOO_DIR) install

    <a name="ex2line37" id="ex2line37">37</a>          $(MAKE) DESTDIR=$(TARGET_DIR) -C $(FOO_DIR) install-strip

    <a name="ex2line38" id="ex2line38">38</a>          rm -Rf $(TARGET_DIR)/usr/man

    <a name="ex2line39" id="ex2line39">39</a>

    <a name="ex2line40" id="ex2line40">40</a>  foo: uclibc ncurses $(TARGET_DIR)/$(FOO_TARGET_BINARY)

    <p>Lines <a href="#ex2line36">36-38</a> defines a target and associated rules

    that install the software inside the target filesystem. It depends on the

    binary file in the source directory, to make sure the software has

    been compiled. It uses the <code>install</code> target of the

    software <code>Makefile</code> by passing a <code>prefix</code>

    been compiled. It uses the <code>install-strip</code> target of the

    software <code>Makefile</code> by passing a <code>DESTDIR</code>

    argument, so that the <code>Makefile</code> doesn't try to install

    the software inside host <code>/usr</code> but inside target

    <code>/usr</code>. After the installation, the