Non-trivial to build with --ninja on yum-based Linux distros

[timClicks]

On Linux distros that use the yum package manager, it's cumbersome to build with ninja because you need to remember to create a symlink. yum installs ninja as ninja-build, but this is hard-coded in the Makefile as ninja.

node/Makefile

Line 127 in a2dcc08

ninja -C out/Release $(NINJA_ARGS)

[jdx]

I'm not sure if there is a convention for this (like CC or CXX env vars), but maybe this could be NINJA? Or NINJA_BIN?