cmake: Small fix to prevent empty module path (#694)

cmake/OCCAConfig.cmake.in

@@ -8,13 +8,16 @@
 # Dependencies that need to be found will depend on the build settings used
 include(CMakeFindDependencyMacro)
 # For some dependencies, we provide custom Find modules, that have been installed next to this file.
-# Temporarily add this directory to the CMAKE_MODULE_PATH
-set(_CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH})
+#   Temporarily add this directory to the CMAKE_MODULE_PATH
+#   Use a variable with an OCCA prefix to store the old value, to prevent the variable being
+#   overwritten by code in the dependencies, executed before the reset
+set(_OCCA_STORE_CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH})
 list(INSERT CMAKE_MODULE_PATH 0 "${CMAKE_CURRENT_LIST_DIR}")
 @exportPackageDependencies@
 # Reset CMAKE_MODULE_PATH
-set(CMAKE_MODULE_PATH ${_CMAKE_MODULE_PATH})
-unset(_CMAKE_MODULE_PATH)
+# Do not use list(REMOVE CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}"), because that would remove all instances, even if they were not added here
+set(CMAKE_MODULE_PATH ${_OCCA_STORE_CMAKE_MODULE_PATH})
+unset(_OCCA_STORE_CMAKE_MODULE_PATH)
 
 # The exported targets are defined in an auto-generated file:
 include( "${CMAKE_CURRENT_LIST_DIR}/OCCATargets.cmake" )