CMake: Add option to use system fmt library

fmt library was added in vendor in 21061c1 commit
for systems with older fmt versions. Now, distributions can choose to link with
their own fmt shared library or use the bundled one.

CMakeLists.txt

@@ -9,6 +9,7 @@ include(GNUInstallDirs)
 # This helps to build vendor projects with or without any patching. Also if any
 # files are changed in vendor projects those can be retained with this option.
 option(ANDROID_TOOLS_PATCH_VENDOR "Patch vendor projects using patches directory" ON)
+option(ANDROID_TOOLS_USE_SYSTEM_FMT "Use system provided fmt library instead of bundled one" OFF)
 
 # Install bash/zsh completion files.
 set(COMPLETION_COMMON_DIR "${CMAKE_INSTALL_FULL_DATADIR}/android-tools/completions")

vendor/CMakeLists.txt

@@ -75,7 +75,13 @@ if(ANDROID_TOOLS_PATCH_VENDOR AND EXISTS "${ANDROID_PATCH_DIR}/")
 endif()
 
 add_subdirectory(boringssl EXCLUDE_FROM_ALL)
-add_subdirectory(fmtlib EXCLUDE_FROM_ALL)
+
+if(ANDROID_TOOLS_USE_SYSTEM_FMT)
+	find_package(fmt CONFIG REQUIRED)
+	message(STATUS "Found fmt: ${fmt_DIR} (version ${fmt_VERSION})")
+else()
+	add_subdirectory(fmtlib EXCLUDE_FROM_ALL)
+endif()
 
 find_package(PkgConfig REQUIRED)
 pkg_check_modules(libbrotlicommon REQUIRED IMPORTED_TARGET libbrotlicommon)