Fix GitHub Actions workflow for macOS/iOS builds and add platform specs to Package.swift

Co-authored-by: fulldecent <[email protected]>

Author: Copilot

.github/workflows/test.yml

@@ -9,26 +9,21 @@ name: Test
 
 jobs:
   test:
-    runs-on: macos-latest
+    runs-on: macos-13
 
     steps:
       - uses: actions/checkout@v4
 
-      - name: Select Xcode version
-        run: >
-          sudo xcode-select -s
-          /Applications/Xcode_15.4.app/Contents/Developer
+      - name: Setup Xcode version
+        uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: '15.4'
 
-      - name: Build
+      - name: Build for macOS
         run: swift build
 
       - name: Run tests
         run: swift test
 
-      - name: Build for iOS Simulator
-        run: |
-          xcodebuild -scheme FDWaveformView \
-            -destination 'platform=iOS Simulator,name=iPhone 15,OS=latest' \
-            build \
-            CODE_SIGNING_REQUIRED=NO \
-            CODE_SIGNING_ALLOWED=NO
+      - name: Build for iOS
+        run: swift build -Xswiftc "-sdk" -Xswiftc "`xcrun --sdk iphonesimulator --show-sdk-path`" -Xswiftc "-target" -Xswiftc "x86_64-apple-ios12.0-simulator"

Package.swift

@@ -5,6 +5,10 @@ import PackageDescription
 
 let package = Package(
     name: "FDWaveformView",
+    platforms: [
+        .iOS(.v12),
+        .macOS(.v10_14)
+    ],
     products: [
         // Products define the executables and libraries a package produces, making them visible to other packages.
         .library(