Build only libsharpyuv inside libwebp

Add comment about cmake version and alphabetize files.
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 80d9e79..90764a5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,6 +26,7 @@
     - name: Setup cmake
       uses: jwlawson/actions-setup-cmake@v1.12
       with:
+        # CMake version 3.17 is required to build libwebp (which libsharpyuv is part of) on macOS.
         cmake-version: '3.17.x'
     - name: Print cmake version
       run: cmake --version
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3efaac1..63415ff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -203,8 +203,8 @@
     src/rawdata.c
     src/read.c
     src/reformat.c
-    src/reformat_libyuv.c
     src/reformat_libsharpyuv.c
+    src/reformat_libyuv.c
     src/scale.c
     src/stream.c
     src/utils.c
diff --git a/ext/libsharpyuv.cmd b/ext/libsharpyuv.cmd
index b4e70c7..e2e3173 100755
--- a/ext/libsharpyuv.cmd
+++ b/ext/libsharpyuv.cmd
@@ -16,6 +16,6 @@
 
 mkdir build
 cd build
-cmake -G Ninja -DBUILD_SHARED_LIBS=OFF -DWEBP_BUILD_CWEBP=OFF -DCMAKE_BUILD_TYPE=Release ..
-ninja
+cmake -G Ninja -DBUILD_SHARED_LIBS=OFF -DCMAKE_BUILD_TYPE=Release ..
+ninja sharpyuv
 cd ../..