Add the --disable-warnings-as-errors flag for building from source
Add the --disable-warnings-as-errors flag for building from source

The latest versions of Xcode on Yosemite come with a version of
Clang that will throw errors when compiling 2.6 from source. Since
MongoDB are unwilling to compensate with backporting the fixes from
2.7/3.0 to 2.6 we'll use their build flag. Without this it's
currently impossible to install from source on a fully up to date
Yosemite.

Closes #800.

Signed-off-by: Dominyk Tiller <53e438f55903875d07efdd98a8aaf887e7208dd3@gmail.com>

UniqMartin/homebrew-versions,coeligena/homebrew-verscustomized,Ashton-W/homebrew-versions,heuermh/homebrew-versions,DomT4/homebrew-versions,jimhe/homebrew-versions