Mark cpuinfo as a build-interface library for c10

This change links the entirety of libcpuinfo into libc10, and removes
libtorch_cpu's direct dependency on libcpuinfo.

This fixes a bug on where on some systems CMake reorders static and
shared libraries in linker invocations, which results in the same object
defined in both libc10 and libtorch_cpu. Since libtorch_cpu already
depends on libc10, it makes sense to make libcpuinfo part of libc10's
interface.

aten/src/ATen/CMakeLists.txt

@@ -642,10 +642,6 @@ if(USE_MKLDNN_ACL)
     list(APPEND ATen_CPU_DEPENDENCY_LIBS ${ACL_LIBRARIES})
 endif()
 
-if(NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^(s390x|ppc64le)$")
-  list(APPEND ATen_CPU_DEPENDENCY_LIBS cpuinfo)
-endif()
-
 if(NOT EMSCRIPTEN AND NOT INTERN_BUILD_MOBILE)
   if(NOT MSVC)
     # Bump up optimization level for sleef to -O1, since at -O0 the compiler

c10/CMakeLists.txt

@@ -106,8 +106,9 @@ if(NOT BUILD_LIBTORCHLESS)
     message(STATUS "don't use NUMA")
   endif()
 
-  if(NOT CMAKE_SYSTEM_PROCESSOR MATCHES "s390x" AND NOT CMAKE_SYSTEM_PROCESSOR MATCHES "ppc64le")
-    target_link_libraries(c10 PRIVATE cpuinfo)
+  if(NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^(s390x|ppc64le)$")
+    target_link_libraries(c10 INTERFACE "$<BUILD_INTERFACE:cpuinfo>")
+    target_link_libraries(c10 PRIVATE "$<LINK_LIBRARY:WHOLE_ARCHIVE,cpuinfo>")
   endif()
 
   find_package(Backtrace)

cmake/Dependencies.cmake

@@ -476,7 +476,6 @@ if(NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^(s390x|ppc64le)$")
     # them into a shared library for Caffe2, so they need PIC.
     set_property(TARGET cpuinfo PROPERTY POSITION_INDEPENDENT_CODE ON)
   endif()
-  list(APPEND Caffe2_DEPENDENCY_LIBS cpuinfo)
 endif()