yocto-check-layer-wrapper: Fix path for oe-init-build-env

We only could run it in top of oe-core dir since it assumed oe-init-build-env
was in cwd, this patch fixes the problem.

[YOCTO #13148]

(From OE-Core rev: 47d7b5fcad127171243cc95c586c2c7f35cfac3b)

(From OE-Core rev: 09e4b9bead32f143f4a685794c4709fe41bf014d)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/yocto-check-layer-wrapper

@@ -30,7 +30,9 @@ cd $base_dir
 
 build_dir=$(mktemp -p $base_dir -d -t build-XXXX)
 
-source oe-init-build-env $build_dir
+this_dir=$(dirname $(readlink -f $0))
+
+source $this_dir/../oe-init-build-env $build_dir
 if [[ $output_log != '' ]]; then
 	yocto-check-layer -o "$output_log" "$*"
 else