The hard-exit path is disabled by default: CRAN Repository Policy
forbids a package from terminating the user's R session, so the released
package must not link _exit(). Builds from source can opt in with
R CMD INSTALL . --configure-args="--enable-hard-exit" (on Windows, set
Sys.setenv(GGML_VK_HARD_EXIT = "1") before installing, because R there
ignores configure.args).
When it is not compiled in, ggml_vulkan_shutdown(hard = TRUE) performs
the normal teardown and emits a warning rather than silently
ignoring the request.