Merge wraps from subprojects into wraps from main project

wraps from subprojects are now merged into the list of wraps from main
project, so they can be used to download dependencies of dependencies
instead of having to promote wraps manually. If multiple projects
provides the same wrap file, the first one to be configured wins.

This also fix usage of sub-subproject that don't have wrap files. We can
now configure B when its source tree is at
`subprojects/A/subprojects/B/`. This has the implication that we cannot
assume that subproject "foo" is at `self.subproject_dir / 'foo'` any
more.

1 files changed, 1 insertions, 1 deletions

diff --git a/test cases/failing/16 extract from subproject/test.json b/test cases/failing/16 extract from subproject/test.json
index 78d45a5..2e32904 100644
--- a/test cases/failing/16 extract from subproject/test.json
+++ b/test cases/failing/16 extract from subproject/test.json
@@ -1,7 +1,7 @@
 {
   "stdout": [
     {
-      "line": "test cases/failing/16 extract from subproject/meson.build:6:0: ERROR: Tried to extract objects from a subproject target."
+      "line": "test cases/failing/16 extract from subproject/meson.build:6:0: ERROR: Tried to extract objects from a different subproject."
     }
   ]
 }