[GITHUB] build-linux: Improve reporting -march value (reactos#8362)

- Make regex stricter.
- Make output more explicit.
- Add comments.

Author: SergeGautherie

.github/workflows/build.yml

@@ -20,7 +20,9 @@ jobs:
     - name: Get RosBE build specifics
       id: get_rosbe_spec
       run: |
-        gcc -march=native -Q --help=target | grep "\-march= " | awk '{print $NF}'
+        # Print actual cpu-type option only.
+        echo -march = $(gcc -march=native -Q --help=target | grep "\-march=  " | awk '{print $NF}')
+        # Take all options/text into account.
         echo march-sha=$(gcc -march=native -Q --help=target | sha1sum | awk '{print $1}') >> $GITHUB_OUTPUT
         echo git-sha=$(git ls-remote https://github.com/zefklop/RosBE.git | grep unix_amd64 | awk '{print $1}') >> $GITHUB_OUTPUT
         wget https://gist.githubusercontent.com/zefklop/b2d6a0b470c70183e93d5285a03f5899/raw/build_rosbe_ci.sh