Fix build errors

The elfio subdirectory addition is due to a change in bpf_conformance

The execute_progress line change is because a build error has been there since
#519 where
https://github.com/vbpf/ebpf-verifier/actions/runs/6275811448/job/17044135123
for example shows (starting at line 27 in the log):

Unknown command: 'ARGS'
NuGet.Commands.CommandException: Unknown command: 'ARGS'
   at NuGet.CommandLine.CommandManager.GetCommand(String commandName)
   at NuGet.CommandLine.CommandLineParser.ParseCommandLine(IEnumerable`1 commandLineArgs)
   at NuGet.CommandLine.Program.MainCore(String workingDirectory, String[] args)
Feeds used:
  https://api.nuget.org/v3/index.json
  C:\Program Files (x86)\Microsoft SDKs\NuGetPackages\

[execute_process](https://cmake.org/cmake/help/latest/command/execute_process.html)
should not have ARGS whereas
[exec_program](https://cmake.org/cmake/help/latest/command/exec_program.html)
does.

Signed-off-by: Dave Thaler <[email protected]>

CMakeLists.txt

@@ -37,7 +37,7 @@ elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
   if (NOT NUGET)
     message("ERROR: You must first install nuget.exe from https://www.nuget.org/downloads")
   else ()
-    execute_process(COMMAND ${NUGET} ARGS install "Boost" -Version 1.81.0 -ExcludeVersion -OutputDirectory ${CMAKE_BINARY_DIR}/packages)
+    execute_process(COMMAND ${NUGET} install "Boost" -Version 1.81.0 -ExcludeVersion -OutputDirectory ${CMAKE_BINARY_DIR}/packages)
     set(BOOST_VERSION 1.81.0)
   endif()
   set(Boost_INCLUDE_DIRS ${CMAKE_BINARY_DIR}/packages/boost/lib/native/include)
@@ -130,6 +130,7 @@ target_compile_options(ebpfverifier PUBLIC "$<$<CONFIG:DEBUG>:${DEBUG_FLAGS}>")
 target_compile_options(ebpfverifier PUBLIC "$<$<CONFIG:RELEASE>:${RELEASE_FLAGS}>")
 target_compile_options(ebpfverifier PUBLIC "$<$<CONFIG:SANITIZE>:${SANITIZE_FLAGS}>")
 
+add_subdirectory("external/bpf_conformance/external/elfio")
 add_subdirectory("external/bpf_conformance/src")
 add_subdirectory("external/libbtf")