Add wasi-sdk-pthread.cmake to docker image to allow enabling it with env (#339)

docker/Dockerfile

@@ -37,6 +37,7 @@ COPY --from=dist /wasi-sdk/share/wasi-sysroot/ /wasi-sysroot/
 COPY --from=dist /wasi-sysroot-clang_rt/lib/wasi /usr/lib/llvm-${LLVM_VERSION}/lib/clang/${LLVM_VERSION}/lib/wasi
 
 ADD docker/wasi-sdk.cmake /usr/share/cmake/wasi-sdk.cmake
+ADD docker/wasi-sdk-pthread.cmake /usr/share/cmake/wasi-sdk-pthread.cmake
 ENV CMAKE_TOOLCHAIN_FILE /usr/share/cmake/wasi-sdk.cmake
 ADD cmake/Platform/WASI.cmake /usr/share/cmake/Modules/Platform/WASI.cmake
 

docker/wasi-sdk-pthread.cmake

@@ -0,0 +1,36 @@
+# Cmake toolchain description file for the wasi-sdk docker image
+
+# This is arbitrary, AFAIK, for now.
+cmake_minimum_required(VERSION 3.4.0)
+
+# To make sure it recognizes the WASI platform
+list(APPEND CMAKE_MODULE_PATH /usr/share/cmake/Modules)
+
+set(CMAKE_SYSTEM_NAME WASI)
+set(CMAKE_SYSTEM_VERSION 1)
+set(CMAKE_SYSTEM_PROCESSOR wasm32)
+set(triple wasm32-wasi-threads)
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -pthread")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pthread")
+# wasi-threads requires --import-memory.
+# wasi requires --export-memory.
+# (--export-memory is implicit unless --import-memory is given)
+set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--import-memory")
+set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--export-memory")
+
+set(CMAKE_C_COMPILER /usr/bin/clang-$ENV{LLVM_VERSION})
+set(CMAKE_CXX_COMPILER /usr/bin/clang++-$ENV{LLVM_VERSION})
+set(CMAKE_ASM_COMPILER /usr/bin/clang-$ENV{LLVM_VERSION})
+set(CMAKE_AR /usr/bin/llvm-ar-$ENV{LLVM_VERSION})
+set(CMAKE_RANLIB /usr/bin/llvm-ranlib-$ENV{LLVM_VERSION})
+set(CMAKE_C_COMPILER_TARGET ${triple})
+set(CMAKE_CXX_COMPILER_TARGET ${triple})
+set(CMAKE_ASM_COMPILER_TARGET ${triple})
+SET(CMAKE_SYSROOT /wasi-sysroot)
+
+# Don't look in the sysroot for executables to run during the build
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+# Only look in the sysroot (not in the host paths) for the rest
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)

docker/wasi-sdk.cmake

@@ -18,6 +18,7 @@ set(CMAKE_AR /usr/bin/llvm-ar-$ENV{LLVM_VERSION})
 set(CMAKE_RANLIB /usr/bin/llvm-ranlib-$ENV{LLVM_VERSION})
 set(CMAKE_C_COMPILER_TARGET ${triple})
 set(CMAKE_CXX_COMPILER_TARGET ${triple})
+set(CMAKE_ASM_COMPILER_TARGET ${triple})
 SET(CMAKE_SYSROOT /wasi-sysroot)
 
 # Don't look in the sysroot for executables to run during the build