Generate PDB files for better debugging on Windows (#16008)

Summary:
1. Unify `build_pytorch_libs.bat`, `setup.py` and `torch/CMakeLists.txt` on the debugging flags with the `CMAKE_BUILD_TYPE` being `Debug`, `Release` and `RelWithDebInfo`.
2. Install PDBs through CMake if they are generated.

Reference:
1. CMake PDB install: https://gitlab.kitware.com/cmake/cmake/issues/18393#note_459199
2. About debugging flags https://stackoverflow.com/a/4662345
3. MSDN page about /DEBUG flag: https://docs.microsoft.com/en-us/cpp/build/reference/debug-generate-debug-info?view=vs-2017
4. MSDN page about /Z{i/I/7}: https://docs.microsoft.com/en-us/cpp/build/reference/z7-zi-zi-debug-information-format?view=vs-2017

Work to do:
- [x] Test the changes work in Release config through this PR
- [ ] <del> Test debug build through https://github.com/pytorch/pytorch/pull/16009 </del>
- [x] Test release build with debugging symbols through #16013

Difficulties:
- [x] Replace /Zi flags with /Z7 (which will be added if DEBUG or RelWithDebInfo is used), as it is not supported by sccache
- [x] Resolve `LINK : fatal error LNK1210: exceeded internal ILK size limit; link with /INCREMENTAL:NO` in the debug build
- [ ] DEBUG build blocked by a MSVC bug. In order to resolve it, we'll need to update the MSVC in CI: https://developercommunity.visualstudio.com/content/problem/225957/fatal-error-lnk1318-unexpected-pdb-error-ok-0.html
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16008

Differential Revision: D13709527

Pulled By: ezyang

fbshipit-source-id: e8365bc75d9ec64099093f7001f83d99a06b196b

modules/detectron/CMakeLists.txt

@@ -12,9 +12,15 @@ if (BUILD_CAFFE2_OPS)
 
     target_link_libraries(caffe2_detectron_ops_gpu caffe2_gpu)
     install(TARGETS caffe2_detectron_ops_gpu DESTINATION lib)
+    if (MSVC)
+      install(FILES $<TARGET_PDB_FILE:caffe2_detectron_ops_gpu> DESTINATION lib OPTIONAL)
+    endif()
   elseif(NOT IOS_PLATFORM)
     add_library(caffe2_detectron_ops SHARED ${Detectron_CPU_SRCS})
     target_link_libraries(caffe2_detectron_ops caffe2)
     install(TARGETS caffe2_detectron_ops DESTINATION lib)
+    if (MSVC)
+      install(FILES $<TARGET_PDB_FILE:caffe2_detectron_ops> DESTINATION lib OPTIONAL)
+    endif()
   endif()
 endif()

modules/module_test/CMakeLists.txt

@@ -12,4 +12,7 @@ if (BUILD_TEST)
 
   target_link_libraries(caffe2_module_test_dynamic caffe2_library)
   install(TARGETS caffe2_module_test_dynamic DESTINATION lib)
+  if (MSVC)
+    install(FILES $<TARGET_PDB_FILE:caffe2_module_test_dynamic> DESTINATION lib OPTIONAL)
+  endif()
 endif()

modules/observers/CMakeLists.txt

@@ -19,6 +19,9 @@ target_include_directories(caffe2_observers PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/.
 target_compile_options(caffe2_observers PRIVATE "-DCAFFE2_BUILD_OBSERVER_LIB")
 install(TARGETS caffe2_observers DESTINATION lib)
 caffe2_interface_library(caffe2_observers caffe2_observers_library)
+if (MSVC)
+  install(FILES $<TARGET_PDB_FILE:caffe2_observers> DESTINATION lib OPTIONAL)
+endif()
 
 if (CAFFE2_CMAKE_BUILDING_WITH_MAIN_REPO)
   set(Caffe2_MODULES ${Caffe2_MODULES} caffe2_observers_library PARENT_SCOPE)