Add support for using the build directory as an installation (#1249)

.github/workflows/build-spack.yml

@@ -138,6 +138,10 @@ jobs:
           fi
           ctest --parallel $(nproc) --timeout 15 --output-on-failure \
             --test-output-size-passed=32768 --test-output-size-failed=1048576
+      - name: Check using build directory as install
+        run: |
+          . ${SPACK_VIEW}/rc
+          CELER_INSTALL_DIR=${PWD}/build ./scripts/ci/test-examples.sh
       - name: Install
         working-directory: build
         run: |

CMakeLists.txt

@@ -263,7 +263,7 @@ celeritas_set_default(CMAKE_INSTALL_MESSAGE LAZY)
 # Output locations for Celeritas products (used by CeleritasUtils.cmake and
 # install code below) will mirror the installation layout
 set(CELERITAS_CMAKE_CONFIG_DIRECTORY
-  "${PROJECT_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR}/cmake")
+  "${PROJECT_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
 set(CELERITAS_HEADER_CONFIG_DIRECTORY
   "${PROJECT_BINARY_DIR}/${CMAKE_INSTALL_INCLUDEDIR}")
 set(CELERITAS_LIBRARY_OUTPUT_DIRECTORY
@@ -558,7 +558,7 @@ endif()
 
 # Where to install configured cmake files
 set(CELERITAS_INSTALL_CMAKECONFIGDIR
-  "${CMAKE_INSTALL_LIBDIR}/cmake/Celeritas")
+  "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
 
 # Build list of CMake files to install
 set(_cmake_files
@@ -585,6 +585,11 @@ install(DIRECTORY "${PROJECT_SOURCE_DIR}/cmake/backport"
   COMPONENT development
 )
 
+# Copy CMake files to support using Celeritas build dir as an install dir
+file(COPY ${_cmake_files}
+  DESTINATION "${CELERITAS_INSTALL_CMAKECONFIGDIR}"
+)
+
 # Export all cache variables that start with CELERITAS_
 set(CELERITAS_EXPORT_VARIABLES)
 macro(celeritas_export_var varname)
@@ -664,6 +669,12 @@ install(EXPORT celeritas-targets
   COMPONENT development
 )
 
+# Export targets to the build tree
+export(EXPORT celeritas-targets
+  FILE "${CELERITAS_CMAKE_CONFIG_DIRECTORY}/CeleritasTargets.cmake"
+  NAMESPACE Celeritas::
+)
+
 if(Celeritas_VERSION VERSION_EQUAL "0.0.0")
   install(CODE "
 message(WARNING \"The Celeritas version was not detected during configuration.