Use symlink to simplify Windows ffmpeg dependency

The FFmpeg dependency is downloaded from two separate zipfiles.

Symlink include/ to expose everything from a single directory, to
simplify the meson script.

PR #2952 <https://github.com/Genymobile/scrcpy/pull/2952>

app/meson.build

@@ -118,10 +118,9 @@ else
         include_directories: include_directories(sdl2_include_dir)
     )
 
-    prebuilt_ffmpeg_shared = meson.get_cross_property('prebuilt_ffmpeg_shared')
-    prebuilt_ffmpeg_dev = meson.get_cross_property('prebuilt_ffmpeg_dev')
-    ffmpeg_bin_dir = meson.current_source_dir() + '/../prebuilt-deps/' + prebuilt_ffmpeg_shared + '/bin'
-    ffmpeg_include_dir = '../prebuilt-deps/' + prebuilt_ffmpeg_dev + '/include'
+    prebuilt_ffmpeg = meson.get_cross_property('prebuilt_ffmpeg')
+    ffmpeg_bin_dir = meson.current_source_dir() + '/../prebuilt-deps/' + prebuilt_ffmpeg + '/bin'
+    ffmpeg_include_dir = '../prebuilt-deps/' + prebuilt_ffmpeg + '/include'
     ffmpeg = declare_dependency(
         dependencies: [
             cc.find_library('avcodec-58', dirs: ffmpeg_bin_dir),

cross_win32.txt

@@ -16,6 +16,5 @@ cpu = 'i686'
 endian = 'little'
 
 [properties]
-prebuilt_ffmpeg_shared = 'ffmpeg-4.3.1-win32-shared'
-prebuilt_ffmpeg_dev = 'ffmpeg-4.3.1-win32-dev'
+prebuilt_ffmpeg = 'ffmpeg-4.3.1-win32-shared'
 prebuilt_sdl2 = 'SDL2-2.0.18/i686-w64-mingw32'

cross_win64.txt

@@ -16,6 +16,5 @@ cpu = 'x86_64'
 endian = 'little'
 
 [properties]
-prebuilt_ffmpeg_shared = 'ffmpeg-4.3.1-win64-shared'
-prebuilt_ffmpeg_dev = 'ffmpeg-4.3.1-win64-dev'
+prebuilt_ffmpeg = 'ffmpeg-4.3.1-win64-shared'
 prebuilt_sdl2 = 'SDL2-2.0.18/x86_64-w64-mingw32'

prebuilt-deps/Makefile

@@ -14,6 +14,7 @@ prepare-ffmpeg-win32:
 	@./prepare-dep https://github.com/Genymobile/scrcpy/releases/download/v1.16/ffmpeg-4.3.1-win32-dev.zip \
 		230efb08e9bcf225bd474da29676c70e591fc94d8790a740ca801408fddcb78b \
 		ffmpeg-4.3.1-win32-dev
+	ln -sf ../ffmpeg-4.3.1-win32-dev/include ffmpeg-4.3.1-win32-shared/
 
 prepare-ffmpeg-win64:
 	@./prepare-dep https://github.com/Genymobile/scrcpy/releases/download/v1.16/ffmpeg-4.3.1-win64-shared.zip \
@@ -22,6 +23,7 @@ prepare-ffmpeg-win64:
 	@./prepare-dep https://github.com/Genymobile/scrcpy/releases/download/v1.16/ffmpeg-4.3.1-win64-dev.zip \
 		2e8038242cf8e1bd095c2978f196ff0462b122cc6ef7e74626a6af15459d8b81 \
 		ffmpeg-4.3.1-win64-dev
+	ln -sf ../ffmpeg-4.3.1-win64-dev/include ffmpeg-4.3.1-win64-shared/
 
 prepare-sdl2:
 	@./prepare-dep https://libsdl.org/release/SDL2-devel-2.0.18-mingw.tar.gz \