Add RB_DEFAULT_PARSER preprocessor macro

This way there is one place to change for switching the default.
This also allows for building the same commit with different cppflags.

1 files changed, 1 insertions, 1 deletions

diff --git a/vm.c b/vm.c
index 4f6b96da5f..e92c823cd7 100644
--- a/vm.c
+++ b/vm.c
@@ -4456,7 +4456,7 @@ rb_ruby_verbose_ptr(void)
     return &cr->verbose;
 }
 
-static bool prism;
+static bool prism = (RB_DEFAULT_PARSER == 1);
 
 bool *
 rb_ruby_prism_ptr(void)