Set backtrace length limit at last

Command line options should have higher precedence than the same
options in shebang and `RUBYOPT`.

internal/cmdlineopt.h

@@ -23,6 +23,7 @@ typedef struct ruby_cmdline_options {
     ruby_features_t features;
     ruby_features_t warn;
     unsigned int dump;
+    int backtrace_length_limit;
 #if USE_RJIT
     struct rb_rjit_options rjit;
 #endif

ruby.c

@@ -217,6 +217,7 @@ cmdline_options_init(ruby_cmdline_options_t *opt)
 #elif defined(YJIT_FORCE_ENABLE)
     opt->features.set |= FEATURE_BIT(yjit);
 #endif
+    opt->backtrace_length_limit = -1;
 
     return opt;
 }
@@ -892,6 +893,7 @@ moreswitches(const char *s, ruby_cmdline_options_t *opt, int envopt)
     VALUE int_enc_name = opt->intern.enc.name;
     ruby_features_t feat = opt->features;
     ruby_features_t warn = opt->warn;
+    int backtrace_length_limit = opt->backtrace_length_limit;
 
     opt->src.enc.name = opt->ext.enc.name = opt->intern.enc.name = 0;
 
@@ -941,6 +943,9 @@ moreswitches(const char *s, ruby_cmdline_options_t *opt, int envopt)
     }
     FEATURE_SET_RESTORE(opt->features, feat);
     FEATURE_SET_RESTORE(opt->warn, warn);
+    if (backtrace_length_limit >= 0) {
+        opt->backtrace_length_limit = backtrace_length_limit;
+    }
 
     ruby_xfree(ptr);
     /* get rid of GC */
@@ -1445,7 +1450,7 @@ proc_long_options(ruby_cmdline_options_t *opt, const char *s, long argc, char **
         char *e;
         long n = strtol(s, &e, 10);
         if (errno == ERANGE || n < 0 || *e) rb_raise(rb_eRuntimeError, "wrong limit for backtrace length");
-        rb_backtrace_length_limit = n;
+        opt->backtrace_length_limit = (int)n;
     }
     else {
         rb_raise(rb_eRuntimeError,
@@ -2329,6 +2334,10 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     }
     if (opt->dump & dump_exit_bits) return Qtrue;
 
+    if (opt->backtrace_length_limit >= 0) {
+        rb_backtrace_length_limit = opt->backtrace_length_limit;
+    }
+
     rb_define_readonly_boolean("$-p", opt->do_print);
     rb_define_readonly_boolean("$-l", opt->do_line);
     rb_define_readonly_boolean("$-a", opt->do_split);