rpncalc - bump flutter

metadata/dev.pesic.rpncalc.yml

@@ -57,10 +57,15 @@ Builds:
     commit: cd5b72329ddda881d144d5e3200a31918e1751a2
     output: build/app/outputs/flutter-apk/app-release.apk
     srclibs:
-      - flutter@2.2.2
-    build:
+      - flutter@3.7.6
+    prebuild:
+      - export PUB_CACHE=$(pwd)/.pub-cache
       - $$flutter$$/bin/flutter config --no-analytics
       - $$flutter$$/bin/flutter packages pub get
+    scandelete:
+      - .pub-cache
+    build:
+      - export PUB_CACHE=$(pwd)/.pub-cache
       - $$flutter$$/bin/flutter packages pub run flutter_launcher_icons:main
       - $$flutter$$/bin/flutter build apk