ECP VELOC Package update (#8910)

* update of veloc & dep versions (replace old non-working versions)

* veloc doesn't work with gcc <= 4.9.3

* explicitly pass MPI to CMake for veloc build

var/spack/repos/builtin/packages/veloc/package.py

@@ -36,7 +36,7 @@ class Veloc(CMakePackage):
     tags = ['ecp']
 
     version('master', branch='master')
-    version('1.0',    '98fe2d9abd2a1b53d7a52267dab91fae')
+    version('1.0',    '98fe2d9abd2a1b53d7a52267dab91fae', preferred=True)
     version('1.0rc1', 'c6db0de56b5b865183b1fa719ac74c1d')
 
     depends_on('boost~atomic~chrono~clanglibcpp~date_time~debug~exception'
@@ -50,6 +50,8 @@ class Veloc(CMakePackage):
     depends_on('axl')
     depends_on('cmake@3.9:', type='build')
 
+    conflicts('%gcc@:4.9.3')
+
     # requires C++11
     def flag_handler(self, name, flags):
         flags = list(flags)
@@ -61,7 +63,8 @@ def cmake_args(self):
         args = [
             "-DWITH_AXL_PREFIX=%s" % self.spec['axl'].prefix,
             "-DWITH_ER_PREFIX=%s" % self.spec['er'].prefix,
-            "-DBOOST_ROOT=%s" % self.spec['boost'].prefix
+            "-DBOOST_ROOT=%s" % self.spec['boost'].prefix,
+            "-DMPI_CXX_COMPILER=%s" % self.spec['mpi'].mpicxx
         ]
 
         return args