Respect BIGNUM_DEBUG defined by command line option

And fixed typo in compilers.yml.

.github/workflows/compilers.yml

@@ -92,7 +92,7 @@ jobs:
           - { key: cppflags, name: NDEBUG,                         value: '-DNDEBUG' }
           - { key: cppflags, name: RUBY_DEBUG,                     value: '-DRUBY_DEBUG' }
           - { key: cppflags, name: ARRAY_DEBUG,                    value: '-DARRAY_DEBUG' }
-          - { key: cppflags, name: BUGNUM_DEBUG,                   value: '-DBUGNUM_DEBUG' }
+          - { key: cppflags, name: BIGNUM_DEBUG,                   value: '-DBIGNUM_DEBUG' }
           - { key: cppflags, name: CCAN_LIST_DEBUG,                value: '-DCCAN_LIST_DEBUG' }
           - { key: cppflags, name: CPDEBUG=-1,                     value: '-DCPDEBUG=-1' }
           - { key: cppflags, name: ENC_DEBUG,                      value: '-DENC_DEBUG' }

bignum.c

@@ -2906,7 +2906,10 @@ bary_divmod(BDIGIT *qds, size_t qn, BDIGIT *rds, size_t rn, const BDIGIT *xds, s
 }
 
 
-#define BIGNUM_DEBUG 0
+#ifndef BIGNUM_DEBUG
+# define BIGNUM_DEBUG (0+RUBY_DEBUG)
+#endif
+
 #if BIGNUM_DEBUG
 #define ON_DEBUG(x) do { x; } while (0)
 static void