#5 system paths not set consistently

[Ed Zaron]

1) The path to NetCDF is set in software/compilers/Local.mk
2) The path to perl is set in the GUI, and it sets some values of the perl location in some scripts.
3) The path to perl is hardwired in install_system
4) gmake is called as a literal in install_script, but most systems do not call gnumake gmake.