We no longer need pre-built ICU libraries

We now build ICU from source in swift-foundation-icu, so we no longer need to
download pre-built ICU libraries.

Author: kateinoigakukun

schemes/main/manifest.json

@@ -1,10 +1,7 @@
 {
   "base-tag": "swift-DEVELOPMENT-SNAPSHOT-2024-09-18-a",
   "build-compiler": false,
-  "icu4c": [
-    "https://github.com/swiftwasm/icu4c-wasi/releases/download/0.10.0/icu4c-wasm32-unknown-wasi.tar.xz",
-    "https://github.com/swiftwasm/icu4c-wasi/releases/download/0.10.0/icu4c-wasm32-unknown-wasip1-threads.tar.xz"
-  ],
+  "icu4c": [],
   "libxml2": [
     "https://github.com/swiftwasm/libxml2-wasm/releases/download/2.0.0/libxml2-wasm32-unknown-wasi.tar.gz",
     "https://github.com/swiftwasm/libxml2-wasm/releases/download/2.0.0/libxml2-wasm32-unknown-wasip1-threads.tar.gz"

tools/build/install-build-sdk.sh

@@ -11,6 +11,7 @@ CURRENT_SCHEME_FILE="$BUILD_SDK_PATH/scheme"
 
 install_libxml2() {
   read -r -a LIBXML2_URLS <<< "$(python3 -c 'import sys, json; print(" ".join(json.load(sys.stdin)["libxml2"]))' < "$SCHEME_DIR/manifest.json")"
+  [ -z "${LIBXML2_URLS+x}" ] && return
   for url in "${LIBXML2_URLS[@]}"; do
     curl -L "$url" | tar xz -C "$BUILD_SDK_PATH"
   done
@@ -22,6 +23,7 @@ install_libxml2() {
 
 install_icu() {
   read -r -a ICU_URLS <<< "$(python3 -c 'import sys, json; print(" ".join(json.load(sys.stdin)["icu4c"]))' < "$SCHEME_DIR/manifest.json")"
+  [ -z "${ICU_URLS+x}" ] && return
   rm -rf "$BUILD_SDK_PATH/icu"
   for url in "${ICU_URLS[@]}"; do
     curl -L "$url" | tar Jx -C "$BUILD_SDK_PATH"