cmake: Use full signature of add_test() command

An executable target in the `COMMAND` option will automatically be
replaced by the location of the executable created at build time.

This change fixes tests for Windows binaries using Wine.

examples/CMakeLists.txt

@@ -12,16 +12,16 @@ endif()
 
 add_executable(ecdsa_example ecdsa.c)
 target_link_libraries(ecdsa_example example)
-add_test(ecdsa_example ecdsa_example)
+add_test(NAME ecdsa_example COMMAND ecdsa_example)
 
 if(SECP256K1_ENABLE_MODULE_ECDH)
   add_executable(ecdh_example ecdh.c)
   target_link_libraries(ecdh_example example)
-  add_test(ecdh_example ecdh_example)
+  add_test(NAME ecdh_example COMMAND ecdh_example)
 endif()
 
 if(SECP256K1_ENABLE_MODULE_SCHNORRSIG)
   add_executable(schnorr_example schnorr.c)
   target_link_libraries(schnorr_example example)
-  add_test(schnorr_example schnorr_example)
+  add_test(NAME schnorr_example COMMAND schnorr_example)
 endif()