install on GRASS

Hp comes with two cc compilers. The one that you may
be using may not have all the features. Try removing
+OS option and see if it works. These flags are specified
for

COMPILE_FLAGS = +O3 +OS -Wp,-H200000

in the HP.trouble.shooting file. You may want
to remove +OS in HP-GRASS/src/CMD/head file.
Nalneesh