Add script to generate dockerfiles for testing

docker/.gitignore

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+Dockerfile-*

docker/generate.lua

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+-- generate.lua --
+-- Run as `lua docker/generate.lua` (from the project root)
+-- Will generate a series of Dockerfiles in this folder (docker) with the format:
+-- Dockerfile-[DISTRO]-[RELEASE]-[LLVM VERSION]-[CMAKE/MAKE]
+--
+-- Example running a build/test (also run from the project root):
+-- docker build -f docker/Dockerfile-ubuntu-18.04-11-cmake
+
+
+local args = {...}
+
+local llvms = {"3.8", "5.0", "6.0", "7", "8", "9", "10", "11", "12"}
+local buildsystems = {"make", "cmake"}
+
+local releasenames = {
+	["16.04"] = "xenial",
+	["18.04"] = "bionic"
+}
+
+local requiresrepo = {
+	["3.8"] = true,
+	["11"] = true,
+	["12"] = true
+}
+
+local argmatrix = {}
+
+for _,llvm in ipairs(llvms) do
+	for _,buildsystem in ipairs(buildsystems) do
+		local release = llvm == "3.8" and "16.04" or "18.04"
+		local options = {
+			LLVM = llvm,
+			DISTRO = "ubuntu",
+			RELEASE = release,
+			RELEASENAME = releasenames[release],
+			BUILDSYSTEM = buildsystem,
+			THREADS = 8
+		}
+		if buildsystem == "cmake" and llvm == "3.8" or llvm == "7" then
+			goto next
+		end
+		table.insert(argmatrix, options)
+		::next::
+	end
+end
+
+function createDockerfile(options)
+	local lines = {}
+	local writeln = function(str)
+		table.insert(lines, str)
+		table.insert(lines, "\n")
+	end
+	local expand = function(str)
+		return str:gsub("@([^@]+)@",function(name)
+			if options[name] then
+				return options[name]
+			else
+				print("Found invalid substitution '"..name.."' in generate.lua docker template")
+				os.exit(2)
+			end
+		end)
+	end
+	writeln[[
+# vim: ft=dockerfile
+
+FROM @DISTRO@:@RELEASE@
+ENV DEBIAN_FRONTEND noninteractive
+
+# Base packages
+RUN apt-get update -qq && apt-get install -qq \
+	apt-utils apt-transport-https ca-certificates \
+	software-properties-common \
+	build-essential \
+	wget git cmake
+# Common Dependencies
+RUN apt-get install -qq libedit-dev libncurses-dev zlib1g-dev
+
+# Install LLVM & Clang
+]]
+
+	if requiresrepo[options.LLVM] then
+		writeln[[
+RUN wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -
+RUN add-apt-repository -y "deb http://apt.llvm.org/@RELEASENAME@/ llvm-toolchain-@RELEASENAME@-@LLVM@ main"
+RUN for i in {1..5}; do apt-get update -qq && break || sleep 15; done
+]]
+	end
+	if options.LLVM == "3.8" then
+		writeln[[
+RUN bash -c "echo 'Package: *' >> /etc/apt/preferences.d/llvm-600" ;\
+    bash -c "echo 'Pin: origin apt.llvm.org' >> /etc/apt/preferences.d/llvm-600" ;\
+    bash -c "echo 'Pin-Priority: 600' >> /etc/apt/preferences.d/llvm-600" ;\
+    cat /etc/apt/preferences.d/llvm-600
+]]
+	end
+
+	writeln[[
+RUN apt-get install -y llvm-@LLVM@-dev clang-@LLVM@ libclang-@LLVM@-dev
+
+COPY . /terra
+]]
+
+	if options.BUILDSYSTEM == "cmake" then
+		writeln[[
+ENV CMAKE_PREFIX_PATH /usr/lib/llvm-@LLVM@:/usr/lib/llvm-@LLVM@
+RUN cd /terra/build && \
+	cmake -DCMAKE_INSTALL_PREFIX=/terra_install .. && \
+	make install -j@THREADS@ && \
+    ctest --output-on-failure -j@THREADS@
+]]
+	elseif options.BUILDSYSTEM == "make" then
+		writeln[[
+RUN cd /terra && make PREFIX=/terra_install LLVM_CONFIG=$(which llvm-config-@LLVM@) CLANG=$(which clang-@LLVM@) test -j@THREADS@
+]]
+	end
+	writeln[[
+#COPY --from=0 /terra_install/* ./dockerbuild/
+]]
+
+	local dockerstring = expand(table.concat(lines))
+	local filename = expand("docker/Dockerfile-@DISTRO@-@RELEASE@-@LLVM@-@BUILDSYSTEM@")
+	local dockerfile = io.open(filename, "w")
+
+	dockerfile:write(dockerstring)
+	dockerfile:close()
+end
+
+for _,options in ipairs(argmatrix) do
+	createDockerfile(options)
+end