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>

include/config.h

@@ -6,7 +6,7 @@
 
 #include "keys.h"
 #include "macros.h"
-#include "util.h"
+#include "util/vec.h"
 
 enum IntrospectionType {
   STRING,
@@ -122,7 +122,8 @@ BUILD(strings, STRINGS, TABLE_STRINGS);
   F(struct Vector, source, STRING_ARRAY, NULL_VEC, name)      \
   F(struct Vector, user_source, STRING_ARRAY, NULL_VEC, name) \
   F(char* NNULLABLE, timefmt, STRING, "%X %x", name)          \
-  F(long long, refresh_rate, NUMBER, 100, name)
+  F(long long, refresh_rate, NUMBER, 100, name)               \
+  F(bool, bypass_shell_login, BOOL, false, name)
 
 BUILD(behavior, BEHAVIOR, TABLE_BEHAVIOR);