do not uninstall nw-gyp on 64 bit Linux

It seems (in installation logs) that nw-gyp does not contain any binary (i.e. compiled) addons.

Thus it's fine if nw-gyp survives 64bit→32bit switch of our Node.js environment on Linux.

.travis.yml

@@ -51,8 +51,6 @@ script:
 - if [ "$platform" = 'linux' ]; then if [ "$NODE_WEBKIT" != "" ]; then npm install nw-gyp -g; fi; fi
 # on Linux rebuild node-sqlite3 for 64 bit node-webkit target (if NODE_WEBKIT is not empty)
 - if [ "$platform" = 'linux' ]; then if [ "$NODE_WEBKIT" != "" ]; then nw-gyp rebuild --target=$NODE_WEBKIT --build-from-source; fi; fi
-# on Linux uninstall nw-gyp for 64 bit if NODE_WEBKIT is not empty
-- if [ "$platform" = 'linux' ]; then if [ "$NODE_WEBKIT" != "" ]; then npm uninstall nw-gyp -g; fi; fi
 - make clean
 # node v0.8 and above provide pre-built 32 bit and 64 bit binaries
 # so here we use the 32 bit ones to also test 32 bit builds