Suppress format-invalid-specifier warnings as our PRIsVALUE generates them

PullRequest: truffleruby/751

Author: eregon

lib/truffle/rbconfig-for-mkmf.rb

@@ -71,6 +71,7 @@
   '-Wno-int-conversion',             # MRI has VALUE defined as long while we have it as void*
   '-Wno-int-to-pointer-cast',        # Same as above
   '-Wno-incompatible-pointer-types', # Fix byebug 8.2.1 compile (st_data_t error)
+  '-Wno-format-invalid-specifier',   # Our PRIsVALUE generates this because compilers ignore printf extensions
   '-ferror-limit=500'
 ].join(' ')