fix binaryen build in docker

Oops I forgot to install cmake and ninja.

Dockerfile

@@ -29,7 +29,8 @@ COPY --from=tinygo-base /tinygo/targets /tinygo/targets
 
 RUN cd /tinygo/ && \
     apt-get update && \
-    apt-get install -y make clang-11 libllvm11 lld-11 && \
+    apt-get install -y make clang-11 libllvm11 lld-11 cmake ninja-build && \
+    mkdir build && \
     make wasi-libc binaryen
 
 # tinygo-avr stage installs the needed dependencies to compile TinyGo programs for AVR microcontrollers.