build: extract CMake plugin/harness modules and add platform build scripts

Split CMakeLists.txt into cmake/Plugin.cmake (production formats and
MinGW link flags) and cmake/Harness.cmake (console test harness with
CTest registration). Add SERUMALT_BUILD_PLUGIN and SERUMALT_BUILD_TESTS
options so production and harness builds are mutually exclusive and
each omits the other's targets.

Add build_linux.sh, build_macos.sh, and build_harness.sh with host
validation, env-overridable build dirs, and explicit option flags.
Rewrite build_windows.sh to use the checked-in mingw64-toolchain.cmake
instead of regenerating it, validate all required tools, and stage
with cmake -E copy_directory.

Broaden .gitignore to cover all build_*/ directories.

build_windows.sh

@@ -7,60 +7,60 @@ set -euo pipefail
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 cd "$SCRIPT_DIR"
 
-TOOLCHAIN_FILE="mingw64-toolchain.cmake"
-BUILD_DIR="build_windows"
-OUTPUT_DIR="SerumAlt_Windows"
+TOOLCHAIN_FILE="$SCRIPT_DIR/mingw64-toolchain.cmake"
+BUILD_DIR="${BUILD_DIR:-$SCRIPT_DIR/build_windows}"
+BUILD_TYPE="${BUILD_TYPE:-Release}"
+OUTPUT_DIR="${OUTPUT_DIR:-$SCRIPT_DIR/SerumAlt_Windows}"
 PLUGIN_NAME="SerumAlt"
+export CMAKE_BUILD_PARALLEL_LEVEL="${CMAKE_BUILD_PARALLEL_LEVEL:-2}"
 
-# 1. Check for the MinGW-w64 cross-compiler and exit if it is not found.
-if ! command -v x86_64-w64-mingw32-g++ >/dev/null 2>&1; then
-    echo "ERROR: x86_64-w64-mingw32-g++ not found." >&2
-    echo "Please install the MinGW-w64 cross-compiler first, e.g.:" >&2
-    echo "    sudo pacman -S mingw-w64-gcc" >&2
+if [[ "$(uname -s)" != Linux ]]; then
+    echo "ERROR: build_windows.sh cross-compiles from Linux using MinGW-w64." >&2
     exit 1
 fi
 
+# 1. Check for the host tools and MinGW-w64 cross-compiler.
+for tool in cmake ninja pkg-config "${CC:-cc}" "${CXX:-c++}" \
+    x86_64-w64-mingw32-gcc x86_64-w64-mingw32-g++ \
+    x86_64-w64-mingw32-windres x86_64-w64-mingw32-ar \
+    x86_64-w64-mingw32-ranlib x86_64-w64-mingw32-strip; do
+    if ! command -v "$tool" >/dev/null 2>&1; then
+        echo "ERROR: $tool not found. See README.md prerequisites." >&2
+        exit 1
+    fi
+done
+
 echo "Found: $(command -v x86_64-w64-mingw32-g++)"
 
-# 2. Generate the CMake toolchain file.
-cat > "$TOOLCHAIN_FILE" <<'EOF'
-set(CMAKE_SYSTEM_NAME Windows)
-set(CMAKE_SYSTEM_PROCESSOR x86_64)
-
-set(CMAKE_C_COMPILER x86_64-w64-mingw32-gcc)
-set(CMAKE_CXX_COMPILER x86_64-w64-mingw32-g++)
-set(CMAKE_RC_COMPILER x86_64-w64-mingw32-windres)
-set(CMAKE_AR x86_64-w64-mingw32-ar)
-set(CMAKE_RANLIB x86_64-w64-mingw32-ranlib)
-set(CMAKE_STRIP x86_64-w64-mingw32-strip)
-
-set(CMAKE_FIND_ROOT_PATH /usr/x86_64-w64-mingw32)
-set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
-set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
-EOF
-
-echo "Wrote toolchain file: $TOOLCHAIN_FILE"
+# 2. Use the checked-in CMake toolchain file without overwriting it.
+if [[ ! -f "$TOOLCHAIN_FILE" ]]; then
+    echo "ERROR: Toolchain file not found: $TOOLCHAIN_FILE" >&2
+    exit 1
+fi
+echo "Using toolchain file: $TOOLCHAIN_FILE"
 
 # 3. Configure with CMake + Ninja (VST3-only cross build, no test harness).
-cmake -S . -B "$BUILD_DIR" -G Ninja \
-    -DCMAKE_BUILD_TYPE=Release \
+echo "Configuring Windows VST3 in $BUILD_DIR ($BUILD_TYPE)..."
+cmake -S "$SCRIPT_DIR" -B "$BUILD_DIR" -G Ninja \
+    -DCMAKE_BUILD_TYPE="$BUILD_TYPE" \
     -DCMAKE_TOOLCHAIN_FILE="$TOOLCHAIN_FILE" \
+    -DSERUMALT_BUILD_PLUGIN=ON \
     -DSERUMALT_BUILD_TESTS=OFF
 
 # 4. Build the VST3 target.
-cmake --build "$BUILD_DIR" --target SerumAlt_VST3
+echo "Building Windows VST3..."
+cmake --build "$BUILD_DIR" --config "$BUILD_TYPE" --target SerumAlt_VST3
 
 # 5. Inject the VST3 moduleinfo.json.
 #    The automatic manifest step is disabled when cross-compiling (see
-#    CMakeLists.txt), because JUCE's manifest helper is a host tool that would
+#    cmake/Plugin.cmake), because JUCE's manifest helper is a host tool that would
 #    otherwise be built as a Windows executable. The moduleinfo content is
-#    deterministic and platform-independent: it depends only on the plugin's
-#    name, manufacturer/plugin codes, and version, so we write the identical
-#    file that the native helper generates. Keep it in sync with the metadata
-#    in CMakeLists.txt (PLUGIN_CODE, PLUGIN_MANUFACTURER_CODE, VERSION).
-VST3_BUNDLE="$BUILD_DIR/${PLUGIN_NAME}_artefacts/Release/VST3/$PLUGIN_NAME.vst3"
+#    deterministic for this Windows plugin: it depends on the plugin's
+#    name, manufacturer/plugin codes, and version, so we write the same metadata
+#    that the native Windows helper generates. Keep it in sync with the metadata
+#    in CMakeLists.txt and cmake/Plugin.cmake, including the vendored VST3 SDK version.
+VST3_BUNDLE="$BUILD_DIR/${PLUGIN_NAME}_artefacts/$BUILD_TYPE/VST3/$PLUGIN_NAME.vst3"
+echo "Writing Windows VST3 manifest..."
 mkdir -p "$VST3_BUNDLE/Contents/Resources"
 cat > "$VST3_BUNDLE/Contents/Resources/moduleinfo.json" <<'EOF'
 {
@@ -73,8 +73,8 @@ cat > "$VST3_BUNDLE/Contents/Resources/moduleinfo.json" <<'EOF'
     "Flags": {
       "Unicode": true,
       "Classes Discardable": false,
-      "Component Non Discardable": false,
-    },
+      "Component Non Discardable": false
+    }
   },
   "Classes": [
     {
@@ -86,12 +86,11 @@ cat > "$VST3_BUNDLE/Contents/Resources/moduleinfo.json" <<'EOF'
       "SDKVersion": "VST 3.7.8",
       "Sub Categories": [
         "Instrument",
-        "Synth",
+        "Synth"
       ],
       "Class Flags": 2,
       "Cardinality": 2147483647,
-      "Snapshots": [
-      ],
+      "Snapshots": []
     },
     {
       "CID": "ABCDEF011234ABCD53616C7453657261",
@@ -102,12 +101,11 @@ cat > "$VST3_BUNDLE/Contents/Resources/moduleinfo.json" <<'EOF'
       "SDKVersion": "VST 3.7.8",
       "Sub Categories": [
         "Instrument",
-        "Synth",
+        "Synth"
       ],
       "Class Flags": 2,
       "Cardinality": 2147483647,
-      "Snapshots": [
-      ],
+      "Snapshots": []
     },
     {
       "CID": "ABCDEF01C0DEF00D53616C7453657261",
@@ -118,17 +116,15 @@ cat > "$VST3_BUNDLE/Contents/Resources/moduleinfo.json" <<'EOF'
       "SDKVersion": "VST 3.7.8",
       "Class Flags": 0,
       "Cardinality": 2147483647,
-      "Snapshots": [
-      ],
-    },
-  ],
+      "Snapshots": []
+    }
+  ]
 }
 EOF
 
-# 6. Copy the resulting .vst3 bundle to SerumAlt_Windows/.
-mkdir -p "$OUTPUT_DIR"
-rm -rf "$OUTPUT_DIR/$PLUGIN_NAME.vst3"
-cp -R "$BUILD_DIR/${PLUGIN_NAME}_artefacts/Release/VST3/$PLUGIN_NAME.vst3" "$OUTPUT_DIR/"
+# 6. Copy the resulting .vst3 bundle to SerumAlt_Windows/ without deleting files.
+echo "Staging Windows VST3 in $OUTPUT_DIR..."
+cmake -E copy_directory "$VST3_BUNDLE" "$OUTPUT_DIR/$PLUGIN_NAME.vst3"
 
 echo
-echo "Done. Windows VST3 plugin at: $SCRIPT_DIR/$OUTPUT_DIR/$PLUGIN_NAME.vst3"
+echo "Done. Windows VST3 plugin at: $OUTPUT_DIR/$PLUGIN_NAME.vst3"