ci: fix the release workflow

1) The path is incorrect because we meant to capture the value of
   `$PWD` _before_ and not after running `popd`

2) The `HOST` value is different on Mac OS (the OS part is "macos"
   instead of the expected "darwin"). There appears to be no way to
   get this from some structured data in stable rustc, so we resort
   to grep that works on all platforms

Author: malor

.github/workflows/release.yml

@@ -77,15 +77,7 @@ jobs:
 
       - id: build
         run: |
-          rustc --print cfg | grep = > rustc.vars
-          source rustc.vars
-
-          if [ -z "${target_env}" ]; then
-            export HOST="${target_arch}-${target_vendor}-${target_os}"
-          else
-            export HOST="${target_arch}-${target_vendor}-${target_os}-${target_env}"
-          fi
-
+          export HOST=$(rustc -vV | grep host: | awk '{print $2}')
           if [ "$HOST" = "$TARGET" ]; then
             cargo build --release --target ${TARGET}
           else
@@ -100,9 +92,8 @@ jobs:
             tar cvzf $ASSET_NAME xsnippet-api
           fi
           gh release upload $RELEASE_TAG $ASSET_NAME
-          popd
-
           echo "asset_path=$PWD/$ASSET_NAME" >> $GITHUB_OUTPUT
+          popd
         env:
           ASSET_NAME: ${{ matrix.name }}
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}