cmake: Move LLVM import to UICommon

To use it, with a modern LLVM (3.9+), set your CMAKE_PREFIX_PATH
to point to the LLVM install folder or to a LLVM build folder.
We're linking ALL of LLVM libs since I don't really know which ones we need.
LTO will take care of sliming the binary size...

CMakeTests/FindLLVM.cmake

@@ -1,44 +0,0 @@
-# This file only exists because LLVM's cmake files are broken.
-# This affects both LLVM 3.4 and 3.5.
-# Hopefully when they fix their cmake system we don't need this garbage.
-
-include(CheckLibraryExists)
-
-list(APPEND LLVM_CONFIG_EXECUTABLES "llvm-config")
-list(APPEND LLVM_CONFIG_EXECUTABLES "llvm-config-3.5")
-list(APPEND LLVM_CONFIG_EXECUTABLES "llvm-config-3.4")
-
-foreach(LLVM_CONFIG_NAME ${LLVM_CONFIG_EXECUTABLES})
-	find_program(LLVM_CONFIG_EXE NAMES ${LLVM_CONFIG_NAME})
-	if (LLVM_CONFIG_EXE)
-		execute_process(COMMAND ${LLVM_CONFIG_EXE} --version OUTPUT_VARIABLE LLVM_PACKAGE_VERSION
-			OUTPUT_STRIP_TRAILING_WHITESPACE )
-		if (LLVM_PACKAGE_VERSION VERSION_GREATER "3.3")
-			execute_process(COMMAND ${LLVM_CONFIG_EXE} --includedir OUTPUT_VARIABLE LLVM_INCLUDE_DIRS
-				OUTPUT_STRIP_TRAILING_WHITESPACE )
-			execute_process(COMMAND ${LLVM_CONFIG_EXE} --ldflags OUTPUT_VARIABLE LLVM_LDFLAGS
-				OUTPUT_STRIP_TRAILING_WHITESPACE )
-			check_library_exists(LLVM-${LLVM_PACKAGE_VERSION} LLVMVerifyFunction "${LLVM_LDFLAGS}" HAVE_DYNAMIC_LLVM_${LLVM_PACKAGE_VERSION})
-			if (HAVE_DYNAMIC_LLVM_${LLVM_PACKAGE_VERSION})
-				set(LLVM_LIBRARIES "${LLVM_LDFLAGS} -lLLVM-${LLVM_PACKAGE_VERSION}")
-				set(CMAKE_REQUIRED_LIBRARIES ${LLVM_LIBRARIES})
-				CHECK_CXX_SOURCE_COMPILES(
-					"#include <llvm-c/Disassembler.h>
-					#include <llvm-c/Target.h>
-					int main(int argc, char **argv)
-					{
-						LLVMInitializeAllTargetInfos();
-						LLVMInitializeAllTargetMCs();
-						LLVMInitializeAllDisassemblers();
-						return 0;
-					}"
-					LLVM_FOUND)
-				unset(CMAKE_REQUIRED_LIBRARIES)
-
-				if (LLVM_FOUND)
-					break()
-				endif()
-			endif()
-		endif()
-	endif()
-endforeach()