Documentation in compilation.md seems to not be correct

Executing npm install better-sqlite3 --build-from-source --sqlite3=/path/to/sqlite-amalgamation as mentioned in the documentation at https://github.com/WiseLibs/better-sqlite3/blob/master/docs/compilation.md does not actually use your sqlite3 amalgamation as I found out by seeing issue #1380.

I think this should be fixed to document some method of compilation that does work (i.e. as mentioned in that same issue, you can overwrite the sqlite3 files in deps to the ones you want to compile and run the build-release script)