use XARGS configuration variable

[Frank Löffler]

The attached patch lets Cactus use a define variable XARGS, much like others (e.g., TAR). This is necessary on systems where the default xargs program cannot be used (e.g., pandora.hpc.lsu.edu). The patch also lets the flesh use this variable, making it compile on these machines.

Keyword:

[Frank Löffler]

Committed as r4968.