qt5: make overriding separatedebuginfo useful

qmake strips before we separate the debuginfo

pkgs/development/libraries/qt-5/hooks/qmake-hook.sh

@@ -22,6 +22,9 @@ qmakePrePhase() {
         qmakeFlags+=( "CONFIG+=release" )
     fi
 
+    # do the stripping ourselves (needed for separateDebugInfo)
+    qmakeFlags+=( "CONFIG+=nostrip" )
+
     qmakeFlags+=( "${qmakeFlags_orig[@]}" )
 }
 prePhases+=" qmakePrePhase"

pkgs/development/libraries/qt-5/modules/qtbase.nix

@@ -213,7 +213,8 @@ stdenv.mkDerivation (finalAttrs: {
     "-shared"
     "-accessibility"
     "-optimized-qmake"
-    "-strip"
+    # for separateDebugInfo
+    "-no-strip"
     "-system-proxies"
     "-pkg-config"