use llvm 12.0.0 release (#178)

* llvm: point at llvmorg-12.0.0 release

* latest wasi-libc

* docker: install cmake from binary, xenials is too old to build llvm

Dockerfile

@@ -6,11 +6,19 @@ FROM ubuntu:xenial
 
 RUN apt-get update \
  && apt-get install -y --no-install-recommends \
+        curl \
+        ca-certificates \
         build-essential \
         clang \
-        cmake \
-        python \
+        python3 \
         git \
         ninja-build \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/*
+
+RUN curl -sSLO https://github.com/Kitware/CMake/releases/download/v3.20.1/cmake-3.20.1-linux-x86_64.tar.gz \
+  && tar xf cmake-3.20.1-linux-x86_64.tar.gz \
+  && rm cmake-3.20.1-linux-x86_64.tar.gz \
+  && mkdir -p /opt \
+  && mv cmake-3.20.1-linux-x86_64 /opt/cmake
+ENV PATH /opt/cmake/bin:$PATH

src/llvm-project

@@ -1 +1 @@
-Subproject commit 176249bd6732a8044d457092ed932768724a6f06
+Subproject commit d28af7c654d8db0b68c175db5ce212d74fb5e9bc

src/wasi-libc

@@ -1 +1 @@
-Subproject commit 378fd4b21aab6d390f3a1c1817d53c422ad00a62
+Subproject commit 659ff414560721b1660a19685110e484a081c3d4