Make sure we use -isystem with Meson on some deps

Otherwise we get warnings on external code.

src/libstore/meson.build

@@ -73,6 +73,7 @@ subdir('build-utils-meson/threads')
 boost = dependency(
   'boost',
   modules : ['container'],
+  include_type: 'system',
 )
 # boost is a public dependency, but not a pkg-config dependency unfortunately, so we
 # put in `deps_other`.
@@ -113,7 +114,7 @@ if aws_s3.found()
       '-laws-cpp-sdk-core',
       '-laws-crt-cpp',
     ],
-  )
+  ).as_system('system')
 endif
 deps_other += aws_s3