Fix libaom Windows build: add explicit source dir to cmake

libaom's CMakeLists.txt uses relative include() paths that require the
source directory to be explicitly specified. Without -S ., cmake cannot
find the included cmake modules, causing configuration to fail.

Author: Hendrik Mennen

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

@@ -19,7 +19,7 @@ protected function build(): void
         cmd()->cd($this->source_dir)
             ->execWithWrapper(
                 $this->builder->makeSimpleWrapper('cmake'),
-                '-B build ' .
+                '-S . -B build ' .
                 '-A x64 ' .
                 "-DCMAKE_TOOLCHAIN_FILE={$this->builder->cmake_toolchain_file} " .
                 '-DCMAKE_BUILD_TYPE=Release ' .