Building lwip v1.4 on ESP8266 generic module

Hi there

I'm using a generic ESP8266 module v2.4 and needed to make a change in the dhcp code.
However, the compiler throws an error when I 'verify' the code.

I'm using eclipse (sloeber) as my IDE and yes I have the lwip Variant option selected as 'v1.4 Open source'.

Here's the error I get..

'Building file: ..\sloeber.ino.cpp'
'Starting C++ compile'
make -C "C:\eclipse/arduinoPlugin/packages/esp8266/hardware/esp8266/2.4.0/tools/sdk/lwip/src" install TOOLS_PATH="C:\eclipse\arduinoPlugin\packages\esp8266\tools\xtensa-lx106-elf-gcc\1.20.0-26-gb404fb9-2/bin/xtensa-lx106-elf-"
'make' is not recognized as an internal or external command,
operable program or batch file.
subdir.mk:98: recipe for target 'sloeber.ino.cpp.o' failed
make: *** [sloeber.ino.cpp.o] Error 1
"C:/eclipse/arduinoPlugin/tools/make/make all" terminated with exit code 2. Build might be incomplete.

01:19:04 Build Failed. 2 errors, 23 warnings. (took 5s.538ms)

It seems to me that something is handling the command wrong! but I am not sure where.
Please help!

Thanks