compatibility with older rsvg-convert

The `--page-width` paramater is only supported since rsvg-convert
version 2.52. For the time being, we avoid it and, instead, add copies
of the launcher icon SVG file with different viewports.

Makefile

@@ -32,7 +32,7 @@ icons-android: android/app/src/main/res/mipmap-hdpi/ic_launcher.png
 assets/launcher_icon.png: assets/launcher_icon.svg
 	rsvg-convert --width=1024 --height=1024 --keep-aspect-ratio assets/launcher_icon.svg > $@
 assets/launcher_icon_adaptive.png: assets/launcher_icon_adaptive.svg
-	rsvg-convert --page-width=1024 --page-height=1024 --width=584 --height=584 --top=220 --left=220 --keep-aspect-ratio assets/launcher_icon_adaptive.svg > $@
+	rsvg-convert --width=1024 --height=1024 --keep-aspect-ratio assets/launcher_icon_adaptive.svg > $@
 android/app/src/main/res/mipmap-hdpi/ic_launcher.png: assets/launcher_icon.png assets/launcher_icon_adaptive.png
 	$(FLUTTER) pub get
 	$(FLUTTER) pub run flutter_launcher_icons:main
@@ -46,12 +46,12 @@ web/icons/Icon-192.png: assets/launcher_icon.svg
 web/icons/Icon-512.png: assets/launcher_icon.svg
 	mkdir -p web/icons/
 	rsvg-convert --width=512 --height=512 --keep-aspect-ratio assets/launcher_icon.svg > $@
-web/icons/Icon-maskable-192.png: assets/launcher_icon_adaptive.svg
+web/icons/Icon-maskable-192.png: assets/launcher_icon_maskable.svg
 	mkdir -p web/icons/
-	rsvg-convert --page-width=192 --page-height=192 --width=150 --height=150 --top=21 --left=21 --keep-aspect-ratio -b '#536dfeff' assets/launcher_icon_adaptive.svg > $@
-web/icons/Icon-maskable-512.png: assets/launcher_icon_adaptive.svg
+	rsvg-convert --width=192 --height=192 --keep-aspect-ratio -b '#536dfeff' assets/launcher_icon_maskable.svg > $@
+web/icons/Icon-maskable-512.png: assets/launcher_icon_maskable.svg
 	mkdir -p web/icons/
-	rsvg-convert --page-width=512 --page-height=512 --width=400 --height=400 --top=56 --left=56 --keep-aspect-ratio -b '#536dfeff' assets/launcher_icon_adaptive.svg > $@
+	rsvg-convert --width=512 --height=512 --keep-aspect-ratio -b '#536dfeff' assets/launcher_icon_maskable.svg > $@
 icons-clean:
 	rm -f android/app/src/main/res/mipmap-*/ic_launcher.png
 	rm -f website/favicon.ico web/favicon.ico web/icons/*.png