Error while debugging a program using debugglibc.sh

[Nisarg Shah <nisargshah323 at gmail dot com>]

OS: Ubuntu 18.04 64-bit
System glibc: 2.27-3ubuntu1
New glibc: built from master branch

Hi all,
I'm following steps from
https://sourceware.org/glibc/wiki/Testing/Builds to install and use a
new glibc alongside the default system installation. After building it
and compiling a simple multithreaded program against it, when I try to
run it under GDB using the debugglibc.sh, I get the following error -

The multithreaded program is copied from
https://timmurphy.org/2010/05/04/pthreads-in-c-a-minimal-working-example/

Steps to compile the program -

SYSROOT=/home/<user>/glibc-master (this is where I installed glibc
using DESTDIR env variable)
gcc \
  -L${SYSROOT}/usr/lib64 \
  -I${SYSROOT}/include \
  --sysroot=${SYSROOT} \
  -Wl,-rpath=${SYSROOT}/lib64 \
  -Wl,--dynamic-linker=${SYSROOT}/lib64/ld-2.18.90.so\
  -pthread /mnt/hd/pthreads_simple.c

Steps followed to run GDB -

$ cd /mnt/hd/glibc-master-build/
$ ./debugglibc.sh /mnt/hd/a.out
Debugging glibc...
Build directory  : /mnt/hd/glibc-master-build/
Source directory : /mnt/hd/glibc
GLIBC Testcase   : /mnt/hd/a.out
GDB Commands     : /mnt/hd/glibc-master-build/debugglibc.gdb
Env vars         :
Reading symbols from /mnt/hd/glibc-master-build//elf/ld.so...done.
/mnt/hd/glibc-master-build/debugglibc.gdb:5: Error in sourced command file:
***The address where /mnt/hd/a.out has been loaded is missing***

I'm not sure how to resolve this. This is the first time I'm
attempting to build/install glib. Any help would be appreciated.

Nisarg