CMake: Instruct compiler to ignore warnings from libs folder - c++

Question

I'm trying to specify to the compiler to ignore all messages + warnings originating from the libs folder, where I keep my external libraries used in my project.
The LLVM library is the main cause of the problem, since the warnings produced fill up the entire screen making it very difficult for me to efficiently identify compile-time errors, etc.
I'm using CMake and have my LLVM 9.0.0 library under the libs folder. I would like to instruct the compiler (using CMake) to ignore all warnings and messages originating from the libs folder.
This is my CMakeLists.txt file:
# General project settings.
cmake_minimum_required(VERSION 3.12.4)
project(ionir)
# Setup compiler flags.
set(CMAKE_CXX_STANDARD 17)
# General project information.
set(PROJECT_URL "https://github.com/ionlang/ir-c")
# Setup source and build directories.
set(SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
set(BIN_DIR ${CMAKE_CURRENT_BINARY_DIR})
option(USE_MD "Use MD instead of MTd" OFF)
if (USE_MD)
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /MD")
#set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /MT")
endif(USE_MD)
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /MTd")
# Setup versioning.
set(VERSION_MAJOR "1")
set(VERSION_MINOR "0")
set(VERSION_PATCH "0")
set(VERSION "$(VERSION_MAJOR).$(VERSION_MINOR).$(VERSION_PATCH)")
# Configure and use LLVM. Also ensures LLVM 9.0.0 is installed.
find_package(LLVM 9.0.0 EXACT REQUIRED CONFIG)
message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
# Include LLVM source directories (for syntax support, etc.). The SYSTEM symbol supposedly marks the directory to supress warnings.
include_directories(SYSTEM ${LLVM_INCLUDE_DIRS}) #---> COMMENTED TO SOLVE CIRCULAR DEPS. PROBLEM.
add_definitions(${LLVM_DEFINITIONS})
# Disable warnings from includes.
#add_library(llvm INTERFACE)
#target_sources(llvm INTERFACE)
#target_include_directories(llvm PRIVATE include/ SYSTEM INTERFACE include/)
# Set source file(s).
file(GLOB_RECURSE SOURCES
"src/*.h"
"src/*.cpp"
)
# Specify that this project is a library.
add_library(${PROJECT_NAME} ${SOURCES})
# Provide include directories to be used in the build command. Position in file matters.
#target_include_directories(${PROJECT_NAME} PRIVATE "src")
include_directories("src")
# Find the libraries that correspond to the LLVM components
# that we wish to use
# llvm_map_components_to_libnames(llvm_libs support core irreader)
# Link against LLVM libraries.
target_link_libraries(${PROJECT_NAME} ${llvm_libs})
# Setup unit testing using Google Test (GTest) if applicable. This binds the CMakeLists.txt on the test project.
option(BUILD_TESTS "Build tests" ON)
if (BUILD_TESTS)
add_subdirectory(libs/googletest)
add_subdirectory(test)
endif()
And below is some of the warnings/messages I'm receiving that are filling up the console.
How can I accomplish this?