old_contents: {
      "targets": [
          {
              "target_name": "zipper",
              "variables": {
                  "libzip%": "0.10"
              },
              "sources": [
                  "src/_zipper.cc",
                  "src/zipper.cpp"
              ],
              "include_dirs": [
                  "deps/libzip-<(libzip)/lib/"
              ],
              "libraries": [
                  "-lzip",
                  "-L../deps/libzip-<(libzip)/lib/.libs/"
              ]
          }
      ]
  }
  
new_contents: {
      "targets": [
          {
              "target_name": "zipper",
              "variables": {
                  "libzip%": "0.10"
              },
              "sources": [
                  "src/_zipper.cc",
                  "src/zipper.cpp"
              ],
              "include_dirs": [
                  "deps/libzip-<(libzip)/lib/"
              ],
              "libraries": [
                  "-lz",
                  "-lzip",
                  "-L../deps/libzip-<(libzip)/lib/.libs/"
              ]
          }
      ]
  }
  
subject: Add -lz.