directly add_subdirectory(nanopb) from torch CMakeLists (#8870)

currently torch/CMakeLists doesn't know how to find nanopb without
some higher-level script (setup.py or build_all.sh) telling it where
to look, which is an obstacle towards fully CMake-ifying libtorch.so.
This change removes that dependency.

tools/cpp_build/build_all.sh

@@ -3,5 +3,4 @@
 set -ex
 SCRIPTPATH="$( cd "$(dirname "$0")" ; pwd -P )"
 source $SCRIPTPATH/build_caffe2.sh
-source $SCRIPTPATH/build_nanopb.sh
 source $SCRIPTPATH/build_libtorch.sh

tools/cpp_build/build_libtorch.sh

@@ -22,6 +22,8 @@ cmake -DUSE_CUDA:BOOL=$USE_CUDA \
       -DCMAKE_BUILD_TYPE:STRING=$BUILD_TYPE \
       -DCMAKE_INSTALL_PREFIX:STRING=$INSTALL_PREFIX \
       -DCMAKE_INSTALL_MESSAGE=NEVER \
+      -Dnanopb_BUILD_GENERATOR:BOOL=OFF \
+      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON \
       -DVERBOSE:BOOL=${VERBOSE:-0} \
       -G "$GENERATE" \
       $PYTORCHPATH/torch

tools/cpp_build/build_nanopb.sh

@@ -1,25 +0,0 @@
-#!/usr/bin/env bash
-
-set -ex
-
-SCRIPTPATH="$( cd "$(dirname "$0")" ; pwd -P )"
-
-pushd $SCRIPTPATH
-source ./build_common.sh
-
-echo "Building nanopb"
-
-mkdir -p $NANOPB_BUILDPATH
-pushd $NANOPB_BUILDPATH
-
-cmake -DCMAKE_BUILD_TYPE:STRING=Release \
-      -DCMAKE_INSTALL_PREFIX:STRING=$INSTALL_PREFIX \
-      -DCMAKE_INSTALL_MESSAGE=NEVER \
-      -Dnanopb_BUILD_GENERATOR:BOOL=OFF \
-      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON \
-      -G "$GENERATE" \
-      $PYTORCHPATH/third_party/nanopb
-$MAKE -j "$JOBS"
-
-popd
-popd

torch/CMakeLists.txt

@@ -37,8 +37,8 @@ find_library(CAFFE2_GPU_LIBRARY caffe2_gpu
 find_library(PROTOBUF_LIBRARY protobuf
   NAMES libprotobuf.a libprotobufd.a libprotobuf.lib libprotobufd.lib
   PATHS ${CAFFE2_BUILD_LIB_DIR} NO_DEFAULT_PATH)
-find_library(NANOPB_LIBRARY protobuf-nanopb
-  PATHS ${NANOPB_BUILD_PATH} NO_DEFAULT_PATH)
+
+add_subdirectory(../third_party/nanopb protobuf-nanopb)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
@@ -291,7 +291,7 @@ target_link_libraries(torch
   ${TORCH_CUDA_LIBRARIES}
   ${CAFFE2_LIBRARY}
   ${PROTOBUF_LIBRARY}
-  ${NANOPB_LIBRARY}
+  protobuf-nanopb
 )
 if(USE_CUDA)
   if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")