PVM Gmake

pvmgmake will hang if it's called by make (rather than

pvmgmake itself)

> pstack 5010
#0 0x0000003180cbe345 in __select_nocancel () from /lib64/tls/libc.so.6
#1 0x0000000000431223 in mxfer ()
#2 0x000000000043203a in mroute ()
#3 0x000000000041fd96 in pvm_recv ()
#4 0x0000000000416cd9 in start_job ()
#5 0x0000000000416e5a in start_remote_job ()
#6 0x000000000040b63a in start_job_command ()
#7 0x000000000040b97a in start_waiting_job ()
#8 0x000000000040c3af in new_job ()
#9 0x00000000004153b3 in update_file ()
#10 0x0000000000415778 in update_goal_chain ()
#11 0x000000000040e691 in main ()

reproduce:
1) > cat Makefile.parent
test:
(tab) pvmgmake -f Makefile.child
> cat Makefile.child
test:
(tab) gcc (...)

2) make -f Makefile.parent
(note: make is a normal gmake without pvm functions)