Change cmake_minimum_required() from 3.17.1 to 3.0 (TriBITSPub/TriBIT…

…S#522)

This is to simulate external projects that call find_package(Trilinos) that
may require an older version of CMake than that is required by
Trilinos/TriBITS.

NOTE: This exposes the error:

---------------------------------------------

CMake Warning (dev) at /ascldap/users/rabartl/Trilinos.base/BUILDS/PR/clang-10.0.0/install/lib/cmake/Kokkos/KokkosConfig.cmake:197 (IF):
  Policy CMP0057 is not set: Support new IN_LIST if() operator.  Run "cmake
  --help-policy CMP0057" for policy details.  Use the cmake_policy command to
  set the policy and suppress this warning.

  IN_LIST will be interpreted as an operator when the policy is set to NEW.
  Since the policy is not set the OLD behavior will be used.
Call Stack (most recent call first):
  /ascldap/users/rabartl/Trilinos.base/BUILDS/PR/clang-10.0.0/install/lib/cmake/Trilinos/TrilinosConfig.cmake:114 (include)
  CMakeLists.txt:8 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Error at /ascldap/users/rabartl/Trilinos.base/BUILDS/PR/clang-10.0.0/install/lib/cmake/Kokkos/KokkosConfig.cmake:197 (IF):
  if given arguments:

    "Kokkos_ENABLE_THREADS" "AND" "NOT" "DEPRECATED_CODE_3" "IN_LIST" "Kokkos_OPTIONS"

  Unknown arguments specified
Call Stack (most recent call first):
  /ascldap/users/rabartl/Trilinos.base/BUILDS/PR/clang-10.0.0/install/lib/cmake/Trilinos/TrilinosConfig.cmake:114 (include)
  CMakeLists.txt:8 (find_package)

-- Configuring incomplete, errors occurred!

---------------------------------------------

reported in #10456 and TRILINOSHD-128

In a later commit, we will update the version of TriBITS that addresses this.

demos/simpleBuildAgainstTrilinos/CMakeLists.txt

@@ -1,6 +1,6 @@
 # CMAKE File for "MyApp" application building against an installed Trilinos
 
-cmake_minimum_required(VERSION 3.17.1)
+cmake_minimum_required(VERSION 3.0)
 
 # Declare project but don't process compilers yet
 #

packages/TrilinosInstallTests/find_package_Trilinos/CMakeLists.txt

@@ -1,4 +1,7 @@
-cmake_minimum_required(VERSION 3.17)
+cmake_minimum_required(VERSION 3.0)
+
+# Disable Kokkos warning about not supporting C++ extensions
+set(CMAKE_CXX_EXTENSIONS OFF)
 
 project(find_package_Trilinos NONE)