move to RAM build

.gitea/actions/prepare-ram-ci/action.yml

@@ -56,6 +56,13 @@ runs:
         NEXUS_NPM_URL="${NEXUS_NPM_URL%/}/"
         NEXUS_NODEJS_URL="${NEXUS_NODEJS_URL%/}/"
 
+        # Resolve the image's stable toolchain before HOME/CARGO_HOME move to RAM.
+        # Keep toolchains in the image; only registry data and build output are ephemeral.
+        RUSTUP_HOME="${RUSTUP_HOME:-$HOME/.rustup}"
+        export RUSTUP_HOME
+        RUST_BIN="$(dirname "$(rustup which --toolchain stable rustc)")"
+        test -x "$RUST_BIN/cargo"
+
         CI_ROOT="$GITHUB_WORKSPACE/.ci"
 
         CI_HOME="$CI_ROOT/home"
@@ -72,7 +79,6 @@ runs:
 
         CARGO_HOME="$CI_ROOT/cargo"
         CARGO_TARGET_DIR="$CI_ROOT/cargo-target"
-        RUSTUP_HOME="$CI_ROOT/rustup"
 
         XDG_CACHE_HOME="$CI_ROOT/xdg-cache"
         XDG_CONFIG_HOME="$CI_ROOT/xdg-config"
@@ -88,7 +94,6 @@ runs:
           "$GRADLE_USER_HOME/init.d" \
           "$CARGO_HOME" \
           "$CARGO_TARGET_DIR" \
-          "$RUSTUP_HOME" \
           "$XDG_CACHE_HOME" \
           "$XDG_CONFIG_HOME" \
           "$XDG_DATA_HOME"
@@ -96,8 +101,7 @@ runs:
         chmod 700 \
           "$CI_HOME" \
           "$GRADLE_USER_HOME" \
-          "$CARGO_HOME" \
-          "$RUSTUP_HOME"
+          "$CARGO_HOME"
 
         cat > "$NPM_CONFIG_USERCONFIG" <<EOF
         registry=$NEXUS_NPM_URL
@@ -181,6 +185,7 @@ runs:
           echo "CARGO_HOME=$CARGO_HOME"
           echo "CARGO_TARGET_DIR=$CARGO_TARGET_DIR"
           echo "RUSTUP_HOME=$RUSTUP_HOME"
+          echo "RUSTUP_TOOLCHAIN=stable"
 
           echo "NVM_NODEJS_ORG_MIRROR=$NEXUS_NODEJS_URL"
 
@@ -191,6 +196,7 @@ runs:
         } >> "$GITHUB_ENV"
 
         {
+          echo "$RUST_BIN"
           echo "$CI_BIN"
           echo "$PNPM_HOME"
         } >> "$GITHUB_PATH"