Remove private prefix in execution root path (#3229)

Author: ghugues

CHANGELOG.md

@@ -56,7 +56,7 @@ END_UNRELEASED_TEMPLATE
 
 ### Fixed
 
-* TBD
+* Fixed incompatible output base causing startup options change: [#3229](https://github.com/MobileNativeFoundation/rules_xcodeproj/pull/3229)
 
 ### Ruleset Development Changes
 

xcodeproj/internal/execution_root.bzl

@@ -4,6 +4,10 @@ def write_execution_root_file(*, actions, bin_dir_path, name):
     """Creates a `File` containing the absolute path to the Bazel execution \
     root.
 
+    If the execution root is under `/private/`, this prefix is stripped so that
+    we don't end up with a different path than what Xcode uses (since we also
+    remove this prefix for Xcode).
+
     Args:
         actions: `ctx.actions`.
         bin_dir_path: `ctx.bin_dir.path`.
@@ -19,6 +23,9 @@ def write_execution_root_file(*, actions, bin_dir_path, name):
         command = """\
 bin_dir_full="$(perl -MCwd -e 'print Cwd::abs_path shift' "{bin_dir}";)"
 execution_root="${{bin_dir_full%/{bin_dir}}}"
+if [[ $execution_root == /private/* ]]; then
+  execution_root="${{execution_root#/private}}"
+fi
 
 echo "$execution_root" > "{output}"
 """.format(