[OSS] Add podspec for libtorch-lite (pytorch#59638)

Summary:
Pull Request resolved: pytorch#59638

ghstack-source-id: 130847775

Test Plan: .

Reviewed By: husthyc, cccclai

Differential Revision: D28966693

fbshipit-source-id: 1b82623279709d0118c0967e2ba730d5dec040cc

ios/LibTorch-Lite.h

@@ -0,0 +1,8 @@
+#ifndef LibTorch_Lite_h
+#define LibTorch_Lite_h
+
+#include <torch/csrc/jit/mobile/import.h>
+#include <torch/csrc/jit/mobile/module.h>
+#include <torch/script.h>
+
+#endif

ios/LibTorch-Lite.podspec

@@ -0,0 +1,36 @@
+Pod::Spec.new do |s|
+    s.name             = 'LibTorch-Lite'
+    s.version          = '1.9.0'
+    s.authors          = 'PyTorch Team'
+    s.license          = { :type => 'BSD' }
+    s.homepage         = 'https://github.com/pytorch/pytorch'
+    s.source           = { :http => "https://ossci-ios.s3.amazonaws.com/libtorch_lite_ios_#{s.version}.zip" }
+    s.summary          = 'The PyTorch C++ library for iOS'
+    s.description      = <<-DESC
+        The PyTorch C++ library for iOS.
+    DESC
+    s.ios.deployment_target = '12.0'
+    s.default_subspec = 'Core'
+    s.subspec 'Core' do |ss|
+        ss.dependency 'LibTorch-Lite/Torch'
+        ss.source_files = 'src/*.{h,cpp,c,cc}'
+        ss.public_header_files = ['src/LibTorch-Lite.h']
+    end
+    s.subspec 'Torch' do |ss|
+        ss.header_mappings_dir = 'install/include/'
+        ss.preserve_paths = 'install/include/**/*.{h,cpp,cc,c}'
+        ss.vendored_libraries = 'install/lib/*.a'
+        ss.libraries = ['c++', 'stdc++']
+    end
+    s.user_target_xcconfig = {
+        'HEADER_SEARCH_PATHS' => '$(inherited) "$(PODS_ROOT)/LibTorch-Lite/install/include/"',
+        'OTHER_LDFLAGS' => '-force_load "$(PODS_ROOT)/LibTorch-Lite/install/lib/libtorch.a" -force_load "$(PODS_ROOT)/LibTorch-Lite/install/lib/libtorch_cpu.a"',
+        'CLANG_CXX_LANGUAGE_STANDARD' => 'c++14',
+        'CLANG_CXX_LIBRARY' => 'libc++'
+    }
+    s.pod_target_xcconfig = {
+        'HEADER_SEARCH_PATHS' => '$(inherited) "$(PODS_ROOT)/LibTorch-Lite/install/include/"',
+        'VALID_ARCHS' => 'x86_64 arm64'
+    }
+    s.library = ['c++', 'stdc++']
+end