build native macOS arm binaries (#541)

.github/workflows/cmake.yml

@@ -25,6 +25,11 @@ jobs:
             arch: x86_64
             toolchain: default.cmake
 
+          - os: macOS-11
+            name: macOS arm64
+            arch: arm64
+            toolchain: macOS-arm64.cmake
+
           - os: windows-latest
             name: Windows x86_64
             arch: x86_64

toolchains/macOS-arm64.cmake

@@ -0,0 +1,23 @@
+# build-macOS-arm64
+
+set(CMAKE_SYSTEM_NAME Darwin)
+set(CMAKE_SYSTEM_PROCESSOR arm64)
+
+set(ZITI_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+
+SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -arch arm64")
+SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -arch arm64")
+
+# for libsodium
+set(triple arm64-apple-macos11)
+execute_process(COMMAND /usr/bin/xcrun -sdk macosx --show-sdk-path
+        OUTPUT_VARIABLE CMAKE_OSX_SYSROOT
+        OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+set(ENV{CFLAGS} "-arch arm64 -isysroot ${CMAKE_OSX_SYSROOT}")
+set(ENV{LDFLAGS} "-arch arm64 -isysroot ${CMAKE_OSX_SYSROOT}")
+
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)