[ncl-install] Error in running ncargf90

[Yuanfu Xie]

Greetings.
I am trying to compile a Fortran code using the command of ncargf90. It returned an error message (see the attached messages). I do not see any file named xcrun on my computer. Would you give me some help on how to resolve this issue? Thank you.
Best regards,
Yuanfu
ncargf90 heun.f90 gfortran -fPIC -fno-range-check -m64 -Wall -fopenmp -O heun.f90 -L/Users/xieyuanfu/plotting/ncl_ncarg-6.4.0-MacOS_10.12_64bit_gnu530/lib -L/opt/X11/lib -lncarg -lncarg_gks -lncarg_c -lXpm -lX11 -lXext -lcairo -lfontconfig -lpixman-1 -lfreetype -lexpat -lpng -lz -lXrender -lbz2xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
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