'libxml/xmlwriter.h' not found after updating to Xcode 7.0.1 and El Capitan

I just updated my MacBook to El Capitan and I have now Xcode 7.0.1. When compiling my NS-3 script, I get the following error (I didn't have before the update):

 In file included from ../src/config-store/model/config-store.cc:11:
    ../src/config-store/model/xml-config.h:5:10: fatal error: 'libxml/xmlwriter.h' file not found
    #include <libxml/xmlwriter.h>
             ^
    1 error generated.
    Waf: Leaving directory `/Users/marcogiordani/final-ns3-mmwave-dir/build'
    Build failed
     -> task in 'ns3-config-store' failed (exit status 1): 
        {task 4469735696: cxx config-store.cc -> config-store.cc.1.o}
    ['/usr/bin/g++', '-Wall', '-Werror', '-Wno-potentially-evaluated-expression', '-Wno-unused-local-typedefs', '-fPIC', '-I.', '-I..', '-I/usr/include/libxml2', '-DNS3_ASSERT_ENABLE', '-DNS3_LOG_ENABLE', '-DHAVE_SYS_IOCTL_H=1', '-DHAVE_IF_NETS_H=1', '-DHAVE_NET_ETHERNET_H=1', '-DHAVE_SQLITE3=1', '../src/config-store/model/config-store.cc', '-c', '-o', 'src/config-store/model/config-store.cc.1.o']

Any suggestion to this issue?

Solution

To whom it may concern, I have just solved the problem by typing on the Terminal:

xcode-select —-install

For some reason, when updating to Xcode 7.0.1, the CommandLineTool hadn’t been updated too, so I did it manually. Now everything works fine.