makeWrapper: accept --argv0 flag (/cc #9562)

By default `makeWrapper` will not set argv[0] (this is a reversion to
the old default behavior). Based on the breakage we have seen from
changing the default, this is what most people want. The `wrapProgram`
function will send `--argv0 '"$0"'` to `makeWrapper`, i.e. it will
continue to pass-through the argv[0] that the wrapper is called with.

pkgs/build-support/setup-hooks/make-wrapper.sh

@@ -2,7 +2,7 @@ makeWrapper() {
     local original=$1
     local wrapper=$2
     local params varName value command separator n fileNames
-    local flagsBefore flags
+    local argv0 flagsBefore flags
 
     mkdir -p "$(dirname $wrapper)"
 
@@ -68,11 +68,17 @@ makeWrapper() {
             n=$((n + 1))
             flagsBefore="$flagsBefore $flags"
         fi
+
+        if test "$p" = "--argv0"; then
+            argv0=${params[$((n + 1))]}
+            n=$((n + 1))
+        fi
     done
 
     # Note: extraFlagsArray is an array containing additional flags
     # that may be set by --run actions.
-    echo exec -a '"$0"' "$original" $flagsBefore '"${extraFlagsArray[@]}"' '"$@"' >> $wrapper
+    echo exec ${argv0:+-a $argv0} "$original" \
+         $flagsBefore '"${extraFlagsArray[@]}"' '"$@"' >> $wrapper
 
     chmod +x $wrapper
 }
@@ -98,5 +104,5 @@ wrapProgram() {
     local prog="$1"
     local hidden="$(dirname "$prog")/.$(basename "$prog")"-wrapped
     mv $prog $hidden
-    makeWrapper $hidden $prog "$@"
+    makeWrapper $hidden $prog --argv0 '"$0"' "$@"
 }