Add subproject wrap files

As a start on getting the repo to build standalone outside of a docker
or bitbake environment, add meson wrap files for most of its
dependencies.

A subproject is still needed for pdbg.  It will take a bit more work as
a subprojects/packagefiles/pdbg/meson.build has to be created for it.

Tested:
Meson gets past these dependencies and then fails on pdbg.

Change-Id: I7379d1feafd00d42f3d38ba08aac6267f9eca76b
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/.gitignore b/.gitignore
index 46d951a..2fcd898 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
 # meson
 /build
 /builddir
+subprojects/*
+!subprojects/*.wrap
+!subprojects/packagefiles