tree-wide: Mark linux and sys includes as system includes

Even though these are in our tree, we should still treat them as
system includes which helps various tools (clangd, iwyu, ...) understand
that these are system includes and <> should be used instead of "".

Author: DaanDeMeyer

LICENSES/README.md

@@ -5,7 +5,7 @@ set -e
 # Exclude following paths from the Coccinelle transformations
 EXCLUDED_PATHS=(
     "src/boot/efi/*"
-    "src/basic/linux/*"
+    "src/basic/include/linux/*"
     # Symlinked to test-bus-vtable-cc.cc, which causes issues with the IN_SET macro
     "src/libsystemd/sd-bus/test-bus-vtable.c"
     "src/libsystemd/sd-journal/lookup3.c"

coccinelle/run-coccinelle.sh

@@ -2053,11 +2053,18 @@ boot_stubs = []
 
 build_dir_include = include_directories('.')
 
-basic_includes = include_directories(
-        'src/basic',
-        'src/fundamental',
-        'src/systemd',
-        '.')
+basic_includes = [
+        include_directories(
+                'src/basic',
+                'src/fundamental',
+                'src/systemd',
+                '.',
+        ),
+        include_directories(
+                'src/basic/include',
+                is_system : true,
+        ),
+]
 
 libsystemd_includes = [basic_includes, include_directories(
         'src/libsystemd/sd-bus',