Unable to make wp76xx with legato 18.01


I am not able to build system binary file for my new module WP7608 (using in mangOH Red). I want to use Legato 18.01 and able to build Legato successfully using make command but while trying to build system for wp7608 using commands . bin/configlegatoenv and make wp76xx getting below error. I am using ova Legato 17.07.2

collect2: error: ld returned 1 exit status
[661/780] Linking C library
ninja: build stopped: subcommand failed.
Makefile:414: recipe for target ‘system_wp76xx’ failed
make: *** [system_wp76xx] Error 1

also tried with new ova Legato 18.02 but getting different build error.
unistd.h file missing.