revert dockerfile, fix build options

Dockerfile

@@ -35,5 +35,5 @@ WORKDIR /root/
 
 COPY . ZoKrates
 
-#RUN cd ZoKrates \
-#    && ./build.sh
+RUN cd ZoKrates \
+    && ./build.sh

build.sh

@@ -4,7 +4,7 @@
 set -e
 
 cd zokrates-cli
-if [ $WITH_LIBSNARK ]; then
+if [ -n "$WITH_LIBSNARK" ]; then
 	cargo build --features libsnark
 else
 	cargo build

zokrates/Cargo.toml

@@ -6,7 +6,7 @@ repository = "https://github.com/JacobEberhardt/ZoKrates.git"
 build = "build.rs"
 
 [features]
-default = ["libsnark"]
+default = []
 libsnark = []
 
 [dependencies]