fixes: improve login environment handling (#114)

* chore(organization): allow nested header and c files

* feat: add shell login "middleware" & etc:
  * lidm now calls `bash` (or other shells, depends on PACKAGE cfg) in
  login mode as a session wrapper to source most env (can be disabled)
  * this fixes a lot of env problems with all `/etc/profile` and more

Extra:
* implemented a musl compatible version of `execvpe` and now lidm should
  search for PATH everywhere it needs to
* `search_path` now also checks if the found binary is properly
  executable
* lidm now uses `confstr` for a decent PATH default if none is found
* logs are unbuffered for cases where debug logs appear empty (exit
  without handlers moment)

* chore: one-time evaluate certain makefile vars

---------

Co-authored-by: grialion <48643945+grialion@users.noreply.github.com>

src/pam.c

@@ -6,6 +6,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "log.h"
 #include "macros.h"
 #include "pam.h"
 #include "sessions.h"
@@ -92,6 +93,10 @@ struct pamh_getenv_status pamh_get_complete_env(pam_handle_t* handle,
   char** raw_envlist = pam_getenvlist(handle);
   if (!raw_envlist) FAIL(PAMH_ERR_ERRNO, "pam_getenvlist");
 
+  char** ptr = raw_envlist;
+  while (*ptr)
+    log_printf("[I] got pam env %s\n", *(ptr++));
+
   struct envpair extra_env[] = {
       {"TERM", getenv("TERM")},
       {"PATH", getenv("PATH")},