CMake: Use toolchain files

CMakeLists.txt

@@ -3,6 +3,8 @@ cmake_minimum_required(VERSION 3.0.0)
 set(ETH_CMAKE_DIR   "${CMAKE_CURRENT_LIST_DIR}/cmake"   CACHE PATH "The the path to the cmake directory")
 list(APPEND CMAKE_MODULE_PATH ${ETH_CMAKE_DIR})
 
+include(EthToolchains)
+
 # Set cmake_policies
 include(EthPolicy)
 eth_policy()

cmake/EthCompilerSettings.cmake

@@ -24,10 +24,6 @@ endif()
 eth_add_cxx_compiler_flag_if_supported(-Wimplicit-fallthrough)
 
 if (("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU") OR ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang"))
-
-	# Use ISO C++14 standard language.
-	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
-
 	# Enables all the warnings about constructions that some users consider questionable,
 	# and that are easy to avoid.  Also enable some extra warning flags that are not
 	# enabled by -Wall.   Finally, treat at warnings-as-errors, which forces developers
@@ -78,10 +74,8 @@ if (("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU") OR ("${CMAKE_CXX_COMPILER_ID}" MA
 			# into errors, which makes sense.
 			# http://stackoverflow.com/questions/21617158/how-to-silence-unused-command-line-argument-error-with-clang-without-disabling-i
 			add_compile_options(-Qunused-arguments)
-		endif()
 
-		if (EMSCRIPTEN)
-			# Do not emit a separate memory initialiser file
+		elseif(EMSCRIPTEN)
 			set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --memory-init-file 0")
 			# Leave only exported symbols as public and aggressively remove others
 			set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fdata-sections -ffunction-sections -Wl,--gc-sections -fvisibility=hidden")

cmake/EthToolchains.cmake

@@ -0,0 +1,8 @@
+if(NOT CMAKE_TOOLCHAIN_FILE)
+  # Use default toolchain file if none is provided.
+  set(
+      CMAKE_TOOLCHAIN_FILE
+      "${CMAKE_CURRENT_LIST_DIR}/toolchains/default.cmake"
+      CACHE FILEPATH "The CMake toolchain file"
+  )
+endif()

cmake/toolchains/default.cmake

@@ -0,0 +1,4 @@
+# Require C++14.
+set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
+set(CMAKE_CXX_EXTENSIONS OFF)

cmake/toolchains/emscripten.cmake

@@ -0,0 +1,2 @@
+include("${CMAKE_CURRENT_LIST_DIR}/default.cmake")
+include("$ENV{EMSCRIPTEN}/cmake/Modules/Platform/Emscripten.cmake")

scripts/travis-emscripten/build_emscripten.sh

@@ -79,9 +79,8 @@ cd $WORKSPACE
 mkdir -p build
 cd build
 cmake \
-  -DCMAKE_TOOLCHAIN_FILE=$EMSCRIPTEN/cmake/Modules/Platform/Emscripten.cmake \
+  -DCMAKE_TOOLCHAIN_FILE=../cmake/toolchains/emscripten.cmake \
   -DCMAKE_BUILD_TYPE=Release \
-  -DEMSCRIPTEN=1 \
   -DBoost_FOUND=1 \
   -DBoost_USE_STATIC_LIBS=1 \
   -DBoost_USE_STATIC_RUNTIME=1 \