mpi: add a broadcast benchmark using synchronized clocks

Based on mpi_sync_clock provided by the PM2 project, detected by the
configure.
The bcast bench will be useful later, when dynamic broadcasts will be
integrated.
2 jobs for !10 with sync-clocks in 10 minutes and 47 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Build
passed #947975
build

00:06:02

 
  Deploy
failed #947976
deploy

00:04:45

 
Name Stage Failure
failed
deploy Deploy
FAIL: perfmodels/regression_based_memset
+ uname -a
+ echo Running on Linux starpu-debian10amd64 4.19.0-8-amd64 #1 SMP Debian 4.19.98-1 (2020-01-26) x86_64 GNU/Linux
Running on Linux starpu-debian10amd64 4.19.0-8-amd64 #1 SMP Debian 4.19.98-1 (2020-01-26) x86_64 GNU/Linux
+ wc -l
+ grep ^FAIL: ../check_2616
+ exit 1
Cleaning up file based variables
ERROR: Job failed: exit status 1