dist/isum.awk doesn't print any output on AIX

[bhuntsman]

On the AIX platform, when running the INSTALL script, only the first few lines of output are printed on the terminal. All of the content that is printed after the loop that is tee(1)'d through the awk program dist/isum.awk is not displayed. However, the install.log is still updated. This appears to be due to the awk program not being particularly portable. Installing GNU awk on AIX and using that instead does work.

Does anyone know enough awk to know the differences between gawk and standard awk to be able to spot the gnu-specific parts?