Use 0/1 for cmake switches.

solc/docker_emscripten/Dockerfile

@@ -62,7 +62,7 @@ RUN git remote add -f solidityjs https://github.com/chriseth/cpp-ethereum
 # TODO this should be a proper merge but somehow causes problems
 # NOTE that we only get the latest commit of that branch
 RUN git cherry-pick solidityjs/solidity-js
-RUN emcmake cmake -DMINER=Off -DETHKEY=Off -DSERPENT=Off -DTESTS=Off -DETHASHCL=Off -DJSCONSOLE=Off -DEVMJIT=Off -DETH_STATIC=1 -DSOLIDITY=ON -DGUI=0 -DCMAKE_CXX_COMPILER=/home/user/emsdk_portable/emscripten/master/em++ -DCMAKE_C_COMPILER=/home/user/emsdk_portable/emscripten/master/emcc
+RUN emcmake cmake -DMINER=0 -DETHKEY=0 -DSERPENT=0 -DTESTS=0 -DETHASHCL=0 -DJSCONSOLE=0 -DEVMJIT=0 -DETH_STATIC=1 -DSOLIDITY=1 -DGUI=0 -DCMAKE_CXX_COMPILER=/home/user/emsdk_portable/emscripten/master/em++ -DCMAKE_C_COMPILER=/home/user/emsdk_portable/emscripten/master/emcc
 RUN emmake make -j 6 soljson
 
 WORKDIR /home/user/cpp-ethereum/solc