Fix build mechanics and handle meson error

app/meson.build

@@ -29,25 +29,34 @@ cc = meson.get_compiler('c')
 
 if not get_option('crossbuild_windows')
 
-    libdir = get_option('local_libav')
-    if libdir != ''
-        lib_avformat = cc.find_library('avformat', dirs : libdir)
-        lib_avcodec = cc.find_library('avcodec', dirs : libdir)
-        lib_avutil = cc.find_library('avutil', dirs : libdir)
-        lib_swscale = cc.find_library('swscale', dirs : libdir)
+    avdir = get_option('local_libav')
+    if avdir != ''
+        message('Using local libav at ' + avdir)
+        libdir = meson.current_source_dir() + '/../' + avdir + '/lib'
+        incdir = '../' + avdir + '/include'
+        ffmpeg = declare_dependency(
+            dependencies: [
+                cc.find_library('avformat', dirs : libdir),
+                cc.find_library('avcodec', dirs : libdir),
+                cc.find_library('avutil', dirs : libdir),
+                cc.find_library('swscale', dirs : libdir)
+            ],
+            include_directories: include_directories(incdir)
+        )
     else
-        lib_avformat = dependency('avformat')
-        lib_avcodec = dependency('avcodec')
-        lib_avutil = dependency('avutil')
-        lib_swscale = dependency('swscale')
+        ffmpeg = declare_dependency(
+            dependencies: [
+                dependency('avformat'),
+                dependency('avcodec'),
+                dependency('avutil'),
+                dependency('swscale')
+            ]
+        )
     endif
 
     # native build
     dependencies = [
-        lib_avformat,
-        lib_avcodec,
-        lib_avutil,
-        lib_swscale,
+        ffmpeg,
         dependency('libpng'),
         dependency('sdl2'),
     ]

mobot.mk

@@ -4,17 +4,19 @@
 
 .DEFAULT_GOAL := scrcpy
 
+AVDIR:=build-libav
+AVLIBDIR:=$(AVDIR)/lib
+AVLIBS:=$(AVLIBDIR)/libavformat.a $(AVLIBDIR)/libavcodec.a $(AVLIBDIR)/libavutil.a $(AVLIBDIR)/libswscale.a
+
 build-ffmpeg:
 	git clone https://github.com/team-mobot/FFmpeg.git build-ffmpeg
 
-AVLIBS:=build-libav/lib/libavformat.a build-libav/lib/libavcodec.a build-libav/lib/libavutil.a build-libav/lib/libswscale.a
 $(AVLIBS): build-ffmpeg
 	# Build Mobot version of FFmpeg and install in subdir libav
 	cd build-ffmpeg && \
 	git checkout encode-png-metadata && \
 	./configure --prefix="../build-libav" \
 				--pkg-config-flags="--static" \
-				--extra-libs="-lpthread -lm" \
 				--enable-gpl --enable-nonfree \
 				--disable-bsfs --disable-filters \
 				--disable-encoders --enable-encoder=png \
@@ -22,11 +24,13 @@ $(AVLIBS): build-ffmpeg
 				--enable-libx264 && \
 	make install-libs install-headers
 
-build-app:
-	meson build-app --buildtype release --strip -Db_lto=true \
-		-Dlocal_libav=${PWD}/build-libav/lib \
-		-Dprebuilt_server=/usr/local/share/scrcpy/scrcpy-server
+build-app: $(AVLIBS)
+	LDFLAGS="-Wl,-lm -Wl,-lpthread" \
+		meson build-app --buildtype release --strip -Db_lto=true \
+		-Dlocal_libav=$(AVDIR) \
+		-Dprebuilt_server=/usr/local/share/scrcpy/scrcpy-server \
+		|| (ret=$$?; rm -rf $@ && exit $$ret)
 
-scrcpy: build-app $(AVLIBS)
+scrcpy: build-app
 	ninja -Cbuild-app
 	cp build-app/app/scrcpy .