build: remove warning until it's reproducible

Also remove the interface it was attached to since it's no longer needed.
This removal simplifies the next commit.

src/CMakeLists.txt

@@ -55,11 +55,6 @@ if(SECP256K1_BUILD_STATIC)
   list(APPEND ${PROJECT_NAME}_installables secp256k1_static)
 endif()
 
-add_library(binary_interface INTERFACE)
-target_compile_definitions(binary_interface INTERFACE
-  $<$<C_COMPILER_ID:MSVC>:_CRT_SECURE_NO_WARNINGS>
-)
-
 add_library(link_library INTERFACE)
 if(SECP256K1_BUILD_SHARED)
   target_link_libraries(link_library INTERFACE secp256k1)
@@ -69,21 +64,17 @@ endif()
 
 if(SECP256K1_BUILD_BENCHMARK)
   add_executable(bench bench.c)
-  target_link_libraries(bench binary_interface link_library)
+  target_link_libraries(bench link_library)
   add_executable(bench_internal bench_internal.c ${internal_obj})
-  target_link_libraries(bench_internal binary_interface)
   add_executable(bench_ecmult bench_ecmult.c ${internal_obj})
-  target_link_libraries(bench_ecmult binary_interface)
 endif()
 
 if(SECP256K1_BUILD_TESTS)
   add_executable(noverify_tests tests.c ${internal_obj})
-  target_link_libraries(noverify_tests binary_interface)
   add_test(noverify_tests noverify_tests)
   if(NOT CMAKE_BUILD_TYPE STREQUAL "Coverage")
     add_executable(tests tests.c ${internal_obj})
     target_compile_definitions(tests PRIVATE VERIFY)
-    target_link_libraries(tests binary_interface)
     add_test(tests tests)
   endif()
 endif()
@@ -92,13 +83,12 @@ if(SECP256K1_BUILD_EXHAUSTIVE_TESTS)
   # Note: do not include $<TARGET_OBJECTS:precomputed> in exhaustive_tests (it uses runtime-generated tables).
   add_executable(exhaustive_tests tests_exhaustive.c ${common_obj})
   target_compile_definitions(exhaustive_tests PRIVATE $<$<NOT:$<CONFIG:Coverage>>:VERIFY>)
-  target_link_libraries(exhaustive_tests binary_interface)
   add_test(exhaustive_tests exhaustive_tests)
 endif()
 
 if(SECP256K1_BUILD_CTIME_TESTS)
   add_executable(ctime_tests ctime_tests.c)
-  target_link_libraries(ctime_tests binary_interface link_library)
+  target_link_libraries(ctime_tests link_library)
 endif()
 
 install(TARGETS ${${PROJECT_NAME}_installables}