Add dependency directories for curl

recipes/cargo/recipe.sh

 GIT=https://github.com/redox-os/cargo.git
 BRANCH=redox_rebase
-BUILD_DEPENDS=(openssl)
+BUILD_DEPENDS=(openssl zlib)
 
 function recipe_build {
+    export DEP_OPENSSL_ROOT="$PWD/../sysroot"
     export OPENSSL_DIR="$PWD/../sysroot"
+    export DEP_Z_ROOT="$PWD/../sysroot"
 }