install with esp-clang & new cache key

.github/workflows/download_esp_clang.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+set -e
+
+ESP_CLANG_VERSION="19.1.2_20250905-3"
+BASE_URL="https://github.com/goplus/espressif-llvm-project-prebuilt/releases/download/${ESP_CLANG_VERSION}"
+
+get_esp_clang_platform() {
+    local platform="$1"
+    local os="${platform%-*}"
+    local arch="${platform##*-}"
+    
+    case "${os}" in
+        "darwin")
+            case "${arch}" in
+                "amd64") echo "x86_64-apple-darwin" ;;
+                "arm64") echo "aarch64-apple-darwin" ;;
+                *) echo "Error: Unsupported darwin architecture: ${arch}" >&2; exit 1 ;;
+            esac
+            ;;
+        "linux")
+            case "${arch}" in
+                "amd64") echo "x86_64-linux-gnu" ;;
+                "arm64") echo "aarch64-linux-gnu" ;;
+                *) echo "Error: Unsupported linux architecture: ${arch}" >&2; exit 1 ;;
+            esac
+            ;;
+        *)
+            echo "Error: Unsupported OS: ${os}" >&2
+            exit 1
+            ;;
+    esac
+}
+
+get_filename() {
+    local platform="$1"
+    local platform_suffix=$(get_esp_clang_platform "${platform}")
+    echo "clang-esp-${ESP_CLANG_VERSION}-${platform_suffix}.tar.xz"
+}
+
+download_and_extract() {
+    local platform="$1"
+    local os="${platform%-*}"
+    local arch="${platform##*-}"
+    local filename=$(get_filename "${platform}")
+    local download_url="${BASE_URL}/${filename}"
+    
+    echo "Downloading ESP Clang for ${platform}..."
+    echo "  URL: ${download_url}"
+    
+    mkdir -p ".sysroot/${os}/${arch}/crosscompile/clang"
+    curl -fsSL "${download_url}" | tar -xJ -C ".sysroot/${os}/${arch}/crosscompile/clang" --strip-components=1
+    
+    if [[ ! -f ".sysroot/${os}/${arch}/crosscompile/clang/bin/clang++" ]]; then
+        echo "Error: clang++ not found in ${platform} toolchain"
+        exit 1
+    fi
+    
+    echo "${platform} ESP Clang ready in .sysroot/${os}/${arch}/crosscompile/clang"
+}
+
+echo "Downloading ESP Clang toolchain version ${ESP_CLANG_VERSION}..."
+
+for platform in "darwin-amd64" "darwin-arm64" "linux-amd64" "linux-arm64"; do
+    download_and_extract "${platform}"
+done
+
+echo "ESP Clang toolchain completed successfully!"