SEGV running test-all in rb_iseq_mark

[mgaudet]

[15938/17478] TestSyntax#test_keyword_rest/home/magaudet/open/ruby_Inliner/test/ruby/test_syntax.rb:120: [BUG] Segmentation fault at 0x000000000103e3
ruby 2.4.0p0 (2016-12-24 revision 57163) [x86_64-linux]

-- Control frame information -----------------------------------------------
c:0027 p:---- s:0156 e:000155 CFUNC  - :eval
c:0026 p:0010 s:0151 e:000150 BLOCK  - /home/magaudet/open/ruby_Inliner/test/ruby/test_syntax.rb:120 [FINISH]

/home/magaudet/open/ruby_Inliner/ruby(rb_vm_bugreport+0x53e) [0x5559befe88fe] vm_dump.c:685
/home/magaudet/open/ruby_Inliner/ruby(rb_bug_context+0xd1) [0x5559befdd901] error.c:426
/home/magaudet/open/ruby_Inliner/ruby(sigsegv+0x3e) [0x5559beed3ffe] signal.c:907
/lib/x86_64-linux-gnu/libpthread.so.0 [0x7efce50313d0]
/home/magaudet/open/ruby_Inliner/ruby(gc_mark_ptr+0x4e) [0x5559bedfe06e] gc.c:1111
/home/magaudet/open/ruby_Inliner/ruby(rb_iseq_mark+0xf5) [0x5559bee29295] iseq.c:128
/home/magaudet/open/ruby_Inliner/ruby(gc_marks_rest+0x74) [0x5559bee02094] gc.c:4629

According to backtrace, crash is here:

      RUBY_MARK_UNLESS_NULL(compile_data->mark_ary);