Update install-node.sh: NODE_FILENAME

[adelmofilho]

When I tried to install the node through this script on my raspberry, independent of the chosen NODE_SHA256 the downloaded node was the same because of the NODE_FILENAME definition, that was hold on linux-x64. With this change, it´s more explicit the need for select the right distribution - This change has revelance once the number of unsucess on installing shiny server on raspberry is high, in general because of this issue.

[ConorIA]

Instead of opening a new PR, can I make a suggestion here:

Lines 8-9 could be replaced by:

case $(uname -m) in
    "x86_64" )
        NODE_SHA256=08e2fcfea66746bd966ea3a89f26851f1238d96f86c33eaf6274f67fce58421a
        NODE_DIST=x64
        ;;
    "armv7l" )
        NODE_SHA256=7a2bb6e37615fa45926ac0ad4e5ecda4a98e2956e468dedc337117bfbae0ac68
        NODE_DIST=armv7l
        ;;
esac

Tested on Rasperry Pi 3 (Rasabian) and 64-bit Manjaro Linux.

Although it looks like there is a merge conflict that needs to be resolved first.