Add Windows builder for libaom library

libaom was listed in lib.json and used as a dependency of libavif, but had
no Windows library builder, causing all Windows builds to fail with:
"library [libaom] is in the lib.json list but not supported to compile"

This adds the missing Windows CMake builder following the same pattern as
other Windows library builders (libavif, libwebp, freetype). The builder
disables docs, examples, tests, and tools for a minimal static build and
uses AOM_TARGET_CPU=generic for portability, matching the Unix builder.

Also adds the static-libs-windows entry to lib.json so the build system
can locate the produced aom.lib artifact.

Author: Hendrik Mennen

config/lib.json

@@ -355,6 +355,9 @@
         "static-libs-unix": [
             "libaom.a"
         ],
+        "static-libs-windows": [
+            "aom.lib"
+        ],
         "cpp-library": true
     },
     "libargon2": {

src/SPC/builder/windows/library/libaom.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\builder\windows\library;
+
+use SPC\store\FileSystem;
+
+class libaom extends WindowsLibraryBase
+{
+    public const NAME = 'libaom';
+
+    protected function build(): void
+    {
+        // reset cmake
+        FileSystem::resetDir($this->source_dir . '\build');
+
+        // start build
+        cmd()->cd($this->source_dir)
+            ->execWithWrapper(
+                $this->builder->makeSimpleWrapper('cmake'),
+                '-B build ' .
+                '-A x64 ' .
+                "-DCMAKE_TOOLCHAIN_FILE={$this->builder->cmake_toolchain_file} " .
+                '-DCMAKE_BUILD_TYPE=Release ' .
+                '-DBUILD_SHARED_LIBS=OFF ' .
+                '-DAOM_TARGET_CPU=generic ' .
+                '-DENABLE_DOCS=OFF ' .
+                '-DENABLE_EXAMPLES=OFF ' .
+                '-DENABLE_TESTDATA=OFF ' .
+                '-DENABLE_TESTS=OFF ' .
+                '-DENABLE_TOOLS=OFF ' .
+                '-DCMAKE_INSTALL_PREFIX=' . BUILD_ROOT_PATH . ' '
+            )
+            ->execWithWrapper(
+                $this->builder->makeSimpleWrapper('cmake'),
+                "--build build --config Release --target install -j{$this->builder->concurrency}"
+            );
+    }
+}