fix typo for glibcxx debug

9 jobs for v2.1rc1 in 6 minutes and 41 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed clang-c++11 #83425
Linux

00:04:51

passed cppcheck #83427
Linux

00:03:27

passed doc #83432
Linux

00:00:09

passed gcc-c++11 #83424
Linux

00:04:34

passed macos-c++11 #83426
Apple

00:01:53

passed VS2015-32-bit #83431
VS2015

00:01:26

passed VS2015-64-bit #83430
VS2015

00:01:31

passed VS2017-32-bit #83429
VS2017

00:01:19

passed VS2017-64-bit #83428
VS2015

00:01:29