NSS dlls was not built with debug information

Hello All,

I have done the following setup to build NSS 3.43:
1) Download and Installed Mozilla build
2) installed gyp and Ninja

D:\apps\nss-prereq\mozilla-build>set set USE_64=1

D:\apps\nss-prereq\mozilla-build>set MOZ_DEBUG_SYMBOLS=1

D:\apps\nss-prereq\mozilla-build>set BUILD_OPT=0

D:\apps\nss-prereq\mozilla-build>start-shell.bat
MozillaBuild Install Directory: D:\apps\nss-prereq\mozilla-build\

$ cd apps/nss-prereq/nss-3.43/nss/
$ ./build.sh
..
run_scanbuild gyp -f ninja --depth=/d/apps/nss-prereq/nss-3.43/nss --generator-output=. -DDEBUG=1 -D_DEBUG=1 -Dtarget_arch=x64 -Dnss_dist_dir=/d/apps/nss-prereq/nss-3.43/dist -Dnss_dist_obj_dir=/d/apps/nss-prereq/nss-3.43/dist/Debug -Dnspr_include_dir=/d/apps/nss-prereq/nss-3.43/dist/Debug/include/nspr -Dnspr_lib_dir=/d/apps/nss-prereq/nss-3.43/dist/Debug/lib /d/apps/nss-prereq/nss-3.43/nss/nss.gyp
ninja: Entering directory `d:/apps/nss-prereq/nss-3.43/nss/out/Debug'

....
[624/1081] D:\apps\nss-prereq\mozilla-build\python\python.exe gyp-win-tool link-with-manifests environment.x64 True d:/apps/nss-prereq/nss-3.43/dist/Debug/lib\softokn3.dll "D:\apps\nss-prereq\mozilla-build\python\python.exe gyp-win-tool link-wrapper environment.x64 False link.exe /nologo /IMPLIB:d:/apps/nss-prereq/nss-3.43/dist/Debug/lib\softokn3.dll.lib /DLL /OUT:d:/apps/nss-prereq/nss-3.43/dist/Debug/lib\softokn3.dll @d:/apps/nss-prereq/nss-3.43/dist/Debug/lib\softokn3.dll.rsp" 2 mt.exe rc.exe "obj\lib\softoken\softokn3.softokn3.dll.intermediate.manifest" obj\lib\softoken\softokn3.softokn3.dll.generated.manifest
.....

Build was successful.

However, following dlls have symbol status 'Binary was not built with debug information':
softokn3.dll
freebl3.dll
nssutil3.dll
sqlite3.dll


I'm not quite familiar with building NSS with gyp and ninja. Do I need to provide some additional flag in order for me to be able to debug NSS (if needed)?

Thanks..