Changes to native source "Compile flags" are not respected

1. Build the attached project for iOS
2. Go to TARGETS > UnityFramework > Build Phases > Compile Sources > Test.m.
3. Note the compile flag -DPLUGIN_IMPORTER_COMPILE_FLAG is set
4. Change the compile flags on Test.m to something else, e.g, "-DSOMETHING_ELSE"
5. Build again (CMD + B)
6. Note the compile flags is still set to -DPLUGIN_IMPORTER_COMPILE_FLAG

Note: If you instead rebuild from scratch (i.e., "replace") the trampoline project, the new compile flag is set correctly.

Expected behavior: The "compile flags" are updated each time the player is built.
Actual behavior: The "compile flags" are only used once, the first time the trampoline project is generated.