Make gitian builds consistent across platforms

Change Linux deps to use a zip archive rather than a gzipped tarball to
match win32
Rename Linux descriptor to gitian-linux.yml to match win32

contrib/gitian-descriptors/README.md

@@ -39,7 +39,7 @@ Once you've got the right hardware and software:
     git pull
     cd ../gitian-builder
     git pull
-    ./bin/gbuild --commit bitcoin=HEAD ../bitcoin/contrib/gitian-descriptors/gitian.yml
+    ./bin/gbuild --commit bitcoin=HEAD ../bitcoin/contrib/gitian-descriptors/gitian-linux.yml
 
     # Build Win32 dependencies: (only needs to be done once, or when dependency versions change)
     ./bin/gbuild --commit bitcoin=HEAD ../bitcoin/contrib/gitian-descriptors/boost-win32.yml

contrib/gitian-descriptors/deps-linux.yml

@@ -7,6 +7,7 @@ architectures:
 - "amd64"
 packages:
 - "unzip"
+- "zip"
 - "pkg-config"
 - "libtool"
 - "faketime"
@@ -59,4 +60,4 @@ script: |
   cd ../..
   #
   cd $STAGING
-  tar -czf $OUTDIR/bitcoin-deps-linux${GBUILD_BITS}-gitian-r1.tar.gz include lib bin host
+  zip -r $OUTDIR/bitcoin-deps-linux${GBUILD_BITS}-gitian-r1.zip include lib bin host

contrib/gitian-descriptors/gitian-linux.yml

@@ -27,8 +27,8 @@ remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"
   "dir": "bitcoin"
 files:
-- "bitcoin-deps-linux32-gitian-r1.tar.gz"
-- "bitcoin-deps-linux64-gitian-r1.tar.gz"
+- "bitcoin-deps-linux32-gitian-r1.zip"
+- "bitcoin-deps-linux64-gitian-r1.zip"
 script: |
   STAGING="$HOME/install"
   OPTFLAGS='-O2'
@@ -38,7 +38,7 @@ script: |
   #
   mkdir -p $STAGING
   cd $STAGING
-  tar xzfm ../build/bitcoin-deps-linux${GBUILD_BITS}-gitian-r1.tar.gz
+  unzip ../build/bitcoin-deps-linux${GBUILD_BITS}-gitian-r1.zip
   cd ../build
   #
   cd bitcoin