Add initial work towards a one-click build setup

We can use some of CMakes built-in systems to ease the required workflow for the whole toolchain. This may eventually allow us to do a single click system where a developer does not need to do anything to get started. If Google can do this (even if slightly scuffed), so can we.

cmake/toolchains/llvm.cmake

@@ -0,0 +1,60 @@
+# TinyAudioLink - Seamlessly transfer Audio between USB capable devices
+# Copyright (C) 2019 Michael Fabian 'Xaymar' Dirks
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+find_program(
+	CLANG_C_COMPILER
+	NAMES
+		clang
+		clang-cl
+		clang++
+		clang-cpp
+	NO_CACHE
+)
+find_program(
+	CLANG_CPP_COMPILER
+	NAMES
+		clang++
+		clang-cpp
+		clang
+		clang-cl
+	NO_CACHE
+)
+find_program(
+	CLANG_LLVM_AR
+	NAMES
+		llvm-ar
+	NO_CACHE
+)
+find_program(
+	CLANG_LLVM_LD_LDD
+	NAMES
+		ld.lld
+	NO_CACHE
+)
+mark_as_advanced(CLANG_C_COMPILER CLANG_CPP_COMPILER CLANG_LLVM_AR CLANG_LLVM_LD_LDD)
+
+set(CMAKE_C_COMPILER "${CLANG_C_COMPILER}")
+set(CMAKE_CXX_COMPILER "${CLANG_CPP_COMPILER}")
+set(CMAKE_AR "${CLANG_LLVM_AR}")
+
+if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.29)
+	set(CMAKE_LINKER_TYPE "LLD")
+else()
+	set(CMAKE_EXE_LINKER_FLAGS_INIT "-fuse-ld=\"${CLANG_LLVM_LD_LDD}\"")
+	set(CMAKE_STATIC_LINKER_FLAGS_INIT "-fuse-ld=\"${CLANG_LLVM_LD_LDD}\"")
+	set(CMAKE_MODULE_LINKER_FLAGS_INIT "-fuse-ld=\"${CLANG_LLVM_LD_LDD}\"")
+	set(CMAKE_SHARED_LINKER_FLAGS_INIT "-fuse-ld=\"${CLANG_LLVM_LD_LDD}\"")
+endif()