### Bug Description PR https://github.com/canonical/snapcraft/pull/5092 added `core24` support for `kde-neon{,-6}`-based snaps. It also added `CMAKE_PREFIX_PATH` as an environment variable to the build environment. However, it separated the multiple paths in the variable with semicolon (`;`), whereas [CMake expects a colon (`:`) as a separator on Linux](https://cmake.org/cmake/help/latest/envvar/CMAKE_PREFIX_PATH.html). https://github.com/canonical/snapcraft/blob/cdf598656caa546db8c5a06815d4edee4fbeb684/snapcraft/extensions/kde_neon.py#L309-L320 However, there is a potential source of confusion here. CMake has: 1. [`CMAKE_PREFIX_PATH` as an environment variable](https://cmake.org/cmake/help/latest/envvar/CMAKE_PREFIX_PATH.html). Paths separated by colon (`:`). With the current code, `prepend_to_env()` will add the wrong separator. 2. [`CMAKE_PREFIX_PATH` as a CMake variable](https://cmake.org/cmake/help/latest/variable/CMAKE_PREFIX_PATH.html#variable:CMAKE_PREFIX_PATH) Paths separated by semicolon (`;`) With the current code, `prepend_to_env()` is not the right function, as it's not and environment variable. The question is, which one of the two are we trying to add? ### To Reproduce Running the following command on any `kde-neon` snap shows that `CMAKE_PREFIX_PATH` is semicolon-separated, instead of colon-separated ``` snapcraft expand-extensions ``` ### Environment Ubuntu 24.04 LTS in destructive mode or LXD. ### snapcraft.yaml ```yaml N/A ``` ### Relevant log output ```shell N/A ``` ### Additional context _No response_