wgrib2 fails to build on Mac OS X 10.11.6

[yurukc]

While I was trying to upgrade ncarg on Mac OS X 10.11.6, I gave the following error message about wgrib2. Then I tried "sudo port clean wgrib2" and "sudo port install wgrib2", respectively but it gave the same error.

Warning: Xcode does not appear to be installed; most ports will likely fail to build.
--->  Computing dependencies for wgrib2
--->  Fetching archive for wgrib2
--->  Attempting to fetch wgrib2-2.0.7_4+gcc7.darwin_15.x86_64.tbz2 from http://nue.de.packages.macports.org/wgrib2
--->  Attempting to fetch wgrib2-2.0.7_4+gcc7.darwin_15.x86_64.tbz2 from http://mse.uk.packages.macports.org/sites/packages.macports.org/wgrib2
--->  Attempting to fetch wgrib2-2.0.7_4+gcc7.darwin_15.x86_64.tbz2 from http://lil.fr.packages.macports.org/wgrib2
--->  Fetching distfiles for wgrib2
--->  Attempting to fetch wgrib2.tgz.v2.0.7 from http://nue.de.distfiles.macports.org/wgrib2
--->  Verifying checksums for wgrib2                                                 
--->  Extracting wgrib2
--->  Applying patches to wgrib2
--->  Configuring wgrib2
--->  Building wgrib2
Error: Failed to build wgrib2: command execution failed

There were also warning notes at the end.

--->  Some of the ports you installed have notes:
  hdf5 has the following notes:
    Mac users may need to set the environment variable "HDF5_USE_FILE_LOCKING" to the five-character string "FALSE" when accessing network mounted files.  This is an
    application run-time setting, not a configure or build setting.  Otherwise errors such as "unable to open file" or "HDF5 error" may be  encountered.
  libidn has the following notes:
    Please be aware that GNU libidn2 is the successor of GNU libidn. It comes with IDNA 2008  
    and TR46 implementations and also provides a compatibility layer for GNU libidn.
  libpsl has the following notes:
    libpsl API documentation is provided by the port 'libpsl-docs'.
  netcdf has the following notes:
    As of version 4.2 c++ and fortran interfaces are separate ports, netcdf-cxx and netcdf-fortran, respectively.
  python27 has the following notes:
    To make this the default Python or Python 2 (i.e., the version run by the 'python' or 'python2' commands), run one or both of:
    
        sudo port select --set python python27
        sudo port select --set python2 python27

Finally I made "sudo port upgrade outdated" and it stopped again while building wgrib2.

Warning: All compilers are either blacklisted or unavailable; defaulting to first fallback option
Warning: All compilers are either blacklisted or unavailable; defaulting to first fallback option
Warning: Xcode does not appear to be installed; most ports will likely fail to build.
--->  Computing dependencies for wgrib2
--->  Building wgrib2
Error: Failed to build wgrib2: command execution failed

[yurukc]

Detailed log file

[jmroot (Joshua Root)]

Warning: Xcode does not appear to be installed; most ports will likely fail to build.

Is Xcode in fact installed? What result do these commands give?

xcode-select -print-path

xcodebuild -version