build: fix node_g target

Checklist

• make -j8 test (UNIX), or vcbuild test nosign (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

build

Description of change

Currently when running make node_g the following error is displayed:

if [ ! -r node -o ! -L  ]; then ln -fs out/Debug/node node_g; fi
/bin/sh: line 0: [: argument expected

It looks like there was a typo for the NODE_EXE where node became lowercase instead of uppercase.