glib-2.0: call os.path.normpath on THISDIR

* some build environments have relative paths in THISDIR, e.g. from OEROOT set in:
  https://github.com/96boards/oe-rpb-manifest/blob/1e3345c26c56f77f3a15a3978f412a25955d2606/conf/bblayers.conf#L4
  and then the paths in filename normalized in:
  filename = os.path.normpath(os.path.join(path, meson.cross.d, element))
  don't match.

* COREBASE used here before didn't have this issue because the value is already
  normalized when set in:
  meta/conf/layer.conf:COREBASE = '${@os.path.normpath("${LAYERDIR}/../")}'

(From OE-Core rev: 7977ff07d181d269bd52f98852d1076b268db614)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/glib-2.0/glib-2.0_2.66.7.bb

@@ -31,7 +31,7 @@ def find_meson_cross_files(d):
     if bb.data.inherits_class('native', d):
         return ""
 
-    thisdir = d.getVar("THISDIR")
+    thisdir = os.path.normpath(d.getVar("THISDIR"))
     import collections
     sitedata = siteinfo_data(d)
     # filename -> found