message: add BLT as dependency and guard cpp14 variant against new versions
diff: @@ -64,6 +64,7 @@ class Axom(CachedCMakePackage, CudaPackage, ROCmPackage):
  variant('examples', default=True, description='Build examples')
  variant('tools', default=True, description='Build tools')
  + # Hard requirement after Axom 0.6.1
  variant('cpp14', default=True, description="Build with C++14 support")
  variant('fortran', default=True, description="Build with Fortran support")
  @@ -92,6 +93,8 @@ class Axom(CachedCMakePackage, CudaPackage, ROCmPackage):
  depends_on("cmake@3.8.2:", type='build')
  depends_on("cmake@3.16.8:", type='build', when="+rocm")
  + depends_on('blt', type='build')
  + depends_on('blt@0.5.0:', type='build', when='@0.6.2:')
  depends_on("mpi", when="+mpi")
  @@ -150,6 +153,9 @@ class Axom(CachedCMakePackage, CudaPackage, ROCmPackage):
  depends_on("py-shroud", when="+devtools")
  depends_on("llvm+clang@10.0.0", when="+devtools", type='build')
  + # Hard requirement after Axom 0.6.1
  + conflicts("~cpp14", when="@0.6.2:")
  +
  # Conduit's cmake config files moved and < 0.4.0 can't find it
  conflicts("^conduit@0.7.2:", when="@:0.4.0")
  @@ -222,7 +228,7 @@ class Axom(CachedCMakePackage, CudaPackage, ROCmPackage):
  entries.append(cmake_cache_string("BLT_EXE_LINKER_FLAGS", flags,
  description))
  - if "+cpp14" in spec:
  + if "+cpp14" in spec and spec.satisfies("@0.6.2:"):
  entries.append(cmake_cache_string("BLT_CXX_STD", "c++14", ""))
  return entries
  @@ -252,6 +258,8 @@ class Axom(CachedCMakePackage, CudaPackage, ROCmPackage):
  entries.append(
  "# cuda_arch could not be determined\n\n")
  + if spec.satisfies("^blt@:0.6.1"):
  + # This is handled internally by BLT now
  if "+cpp14" in spec:
  cudaflags += " -std=c++14"
  else:
  